B Pharmacy 1st Semester Pharmaceutical Inorganic Chemistry Important Question Answer

B.Pharmacy 1st Semester Pharmaceutical Inorganic Chemistry 

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Pharmaceutical Inorganic Chemistry Important Question Answer  

Pharmaceutical Inorganic Chemistry Very Short Question Answer [2 Marks] 

1. Define the term impurity: 
An impurity is any unwanted substance present within a pharmaceutical substance that affects its quality, safety, or efficacy. 

2. Classify residual solvents: 
Residual solvents are classified into: 

• Class 1 (to be avoided) 

• Class 2 (to be limited) 

• Class 3 (low toxic potential) 

3. Draw the structure of lead-dithizone complex: 
 

 

(Structure: Pb(C13H12N4S2)) – Dithizone chelates with lead to form a colored complex. 

4. In limit test for iron, __________ prevents the precipitate of iron as Fe(OH)₃: 
(NH₃ solution) 

5. Choose the correct answer (Bronsted-Lowry acid): 
a) proton donor 

6. Major anion of ICF is: 
Phosphate (HPO₄²⁻) 

7. True/False: In White and Vincent method, sodium chloride is used to adjust the pH: 
False 
(It is used to adjust tonicity.) 

8. _______% sodium chloride solution is isotonic to plasma: 
0.9% 

9. Write down the formula of blue vitriol: 
CuSO₄·5H₂O 

10. ______ method is used for ammonium chloride: 
Formol titration method 

11. ______ is an example of expectorant: 
Potassium iodide 

12. Povidone iodine is used as: 
a) antiseptic 

13. The acid neutralizing capacity of an antacid is at least: 
a) 5 meq. of HCl per dosage unit 

14. Saline cathartics should not be given to: 
c) patients on low sodium diet 

15. Which is not a type of gas-filled detector? 
c) Semiconductor detector 

16. Which is not used as an antidote? 
a) Ferrous sulphate 

17. Correct statement for handling radioactive materials: 
d) All of the above 

18. Sodium metabisulfite is used as: 
d) antioxidant 

19. Emetics: 
a) Stimulate CTZ centre 

20. True/False: Potassium iodide is used as expectorant: 
True 

21. Define buffering: 
Buffering is the ability of a solution to resist changes in pH upon addition of an acid or base. 

22. What is meant by primary standard substance? 
A primary standard is a substance of known high purity used to prepare standard solutions for titrations. 

23. Define the term limit test: 
A limit test is a quantitative or semi-quantitative test designed to identify and control small quantities of impurities in drugs. 

24. Which reagent is used in the limit test of chloride? 
Silver nitrate (AgNO₃) 

25. Antidote in cyanide poisoning: 
c) Both a and b (Sodium thiosulphate and Sodium nitrate) 

26. Function of sodium chloride in ORS: 
To maintain electrolyte balance and restore fluid loss in dehydration. 

27. True/False: Kaolin is used as an anti-diarrheal agent: 
True 

28. Define the term expectorant: 
Expectorants are agents that promote the removal of mucus from the respiratory tract. 

29. Which is not a saline cathartic? 
c) Magnesium carbonate 

30. Which of the following is a systemic acidifier? 
a) Ammonium chloride 

31. State the use of zinc oxide: 
Zinc oxide is used as a mild astringent, skin protectant, and in diaper rash creams. 

32. What is meant by antidote? 
An antidote is a substance that counteracts the effects of a poison. 

33. Sodium fluoride is used to prevent: 
Dental caries 

34. Define radiopharmaceuticals: 
Radiopharmaceuticals are radioactive compounds used for diagnosis or therapy in nuclear medicine. 

35. True/False: NaCl is used in isotonic solution to match plasma concentration: 
True 

36. Role of sodium metabisulphite in pharmaceutical preparation: 
Acts as an antioxidant to prevent oxidation of drug substances. 

37. Which of the following is used as a gastric antacid? 
a) Magnesium hydroxide 

38. Name one official compound of iron: 
Ferrous sulphate (FeSO₄·7H₂O) 

39. True/False: Activated charcoal is used as an adsorbent: 
True 

40. Role of phosphate buffer in pharmaceutical preparations: 
Maintains the pH of the formulation for stability and bioavailability. 

41. Define isotonic solution: 
A solution having the same osmotic pressure as body fluids like blood plasma. 

42. Two pharmaceutical uses of sodium thiosulphate: 

1. Antidote in cyanide poisoning 

2. Used in iodine titrations (analytical reagent) 

43. Define the term “antidote”: 
A substance that neutralizes or counteracts the effect of a poison. 

44. What is meant by acidifiers? Give one example: 
Acidifiers are agents that increase gastric acid production. Example: Ammonium chloride 

45. Which of the following is an expectorant? 
a) Potassium iodide 

46. True/False: Boric acid is used as an eye wash: 
True 

47. What are emetics? 
Emetics are drugs that induce vomiting by stimulating the vomiting center or gastric mucosa. 

48. Name any one antimicrobial agent: 
Povidone iodine 

49. Which of the following is a systemic alkalizer? 
a) Sodium bicarbonate 

50. Name one source of impurity in pharmaceutical substances: 
Raw materials or reagents used in manufacturing 

51. Define buffering capacity: 
It is the amount of acid or base that a buffer can neutralize without a significant change in pH. 

52. Method used for assay of ammonium chloride: 
Formol titration 

53. Blue vitriol is: 
a) CuSO₄·5H₂O 

54. One pharmaceutical use of sodium nitrite: 
Used as an antidote in cyanide poisoning. 

55. True/False: G.M. Counter is a type of gas-filled radiation detector: 
True 

56. Mention one example of radiopharmaceutical: 
Sodium iodide (I-131) 

57. Use of sodium metabisulfite in pharmacy: 
Used as an antioxidant to prevent degradation of formulations. 

58. Which of the following is not an antacid? 
c) Zinc oxide 

59. Name any one gas used in radioactive scanning: 
Xenon-133 (Xe-133) 

60. Define haematinics: 
Haematinics are substances that increase the hemoglobin level and help in the formation of blood. 

 

 

 

Pharmaceutical Inorganic Chemistry Short Question Answer [5 Marks] 

1. Define and classify impurities in pharmaceutical substances. 

Definition: 
Impurities are unwanted chemical substances that remain with the active pharmaceutical ingredients (APIs) or develop during formulation or upon aging. They affect the safety, efficacy, and quality of the pharmaceutical product. 

Classification of Impurities: 

1. Organic Impurities: 

1. Arise from starting materials, intermediates, or degradation products. 

2. E.g., by-products, residual solvents. 

2. Inorganic Impurities: 

1. Originate from manufacturing processes. 

2. E.g., reagents, catalysts, heavy metals, sulphated ash. 

3. Residual Solvents: 

1. Organic volatile chemicals used in or produced during the manufacturing process. 

2. Classified by ICH as: 

1. Class 1 (to be avoided) 

2. Class 2 (to be limited) 

3. Class 3 (low toxic potential) 

4. Environmental Impurities: 

1. Introduced during handling, such as dust, microorganisms, or moisture. 

5. Degradation Products: 

1. Formed due to environmental conditions like heat, light, pH. 

Sources of Impurities: 

• Raw materials 

• Manufacturing process 

• Storage conditions 

• Packaging materials 

• Cross-contamination 

Importance of Controlling Impurities: 

• To ensure safety and therapeutic efficacy. 

• Regulatory requirements (as per ICH and pharmacopoeias). 

• To avoid adverse effects or toxicity. 

Conclusion: 
Understanding and controlling impurities in pharmaceutical substances is essential for quality assurance. Pharmacopoeial methods like limit tests and analytical techniques (e.g., HPLC, GC) are used for detecting and quantifying impurities. 

2. Write the preparation, properties and uses of boric acid. 

Preparation: 
Boric acid (H₃BO₃) is prepared by reacting borax (Na₂B₄O₇·10H₂O) with sulfuric acid: 
Na₂B₄O₇ + H₂SO₄ + 5H₂O → 4H₃BO₃ + Na₂SO₄ 

Properties: 

• White crystalline powder 

• Weak monobasic acid 

• Soluble in hot water and alcohol 

• Antiseptic and antifungal activity 

• Slightly acidic pH (~5) 

Uses: 

• Used as a buffer in ophthalmic solutions 

• Acts as a mild antiseptic for skin and eyes 

• Used in dusting powders 

• As a pH adjuster and preservative in pharmaceuticals 

• Employed in manufacture of borate buffer 

 

3. Define primary standard. Give properties and examples. 

Definition: 
A primary standard is a reagent that is pure, stable, non-hygroscopic, and has a known stoichiometry, used for preparing standard solutions for titration. 

Properties: 

• High purity 

• Stable in air 

• Soluble in the solvent used 

• High equivalent weight 

• Non-hygroscopic 

• Easily dried without decomposition 

Examples: 

• Sodium carbonate (Na₂CO₃) 

• Potassium hydrogen phthalate (KHP) 

• Potassium dichromate (K₂Cr₂O₇) 

 

4. What are antacids? Classify them and give examples. 

Definition: 
Antacids are substances that neutralize excess gastric acid and relieve symptoms of acidity and heartburn. 

Classification: 

1. Systemic antacids: 

• Absorbed into the blood 

• Rapid action but systemic alkalosis possible 

• Example: Sodium bicarbonate 

2. Non-systemic antacids: 

• Not absorbed 

• Local action only 

• Example: Magnesium hydroxide, Aluminium hydroxide 

Examples: 

• Sodium bicarbonate 

• Magnesium hydroxide 

• Aluminium hydroxide 

• Magnesium trisilicate 

• Calcium carbonate 

 

5. Write the identification test for sulphate and chloride. 

Chloride Test: 

• Reagent: Silver nitrate solution (AgNO₃) 

• Add AgNO₃ to the solution → White precipitate of AgCl 

• Confirm by solubility in ammonium hydroxide 

Reaction: 
Cl⁻ + AgNO₃ → AgCl ↓ (white ppt) 

Sulphate Test: 

• Reagent: Barium chloride (BaCl₂) in presence of dilute HCl 

• Add BaCl₂ → White precipitate of BaSO₄ 

• Confirm by insolubility in HCl 

Reaction: 
SO₄²⁻ + BaCl₂ → BaSO₄ ↓ (white ppt) 

 

6. Explain the limit test for iron. 

Purpose: 
To detect and control the amount of iron impurity in pharmaceuticals. 

Principle: 
Iron in the sample reacts with thioglycolic acid in acidic medium to form a purple-colored complex. The color intensity is compared with that of a standard. 

Procedure: 

• Take test solution in Nessler cylinder 

• Add citric acid and thioglycolic acid 

• Make alkaline with ammonia solution 

• Allow to stand for 5 minutes 

• Compare with standard iron solution 

Result Interpretation: 
The test solution should not be more intensely colored than the standard. 

 

7. Write the preparation and use of sodium thiosulphate. 

Preparation: 
By boiling sodium sulphite with sulphur: 
Na₂SO₃ + S → Na₂S₂O₃ 

Properties: 

• White crystalline powder 

• Soluble in water 

• Slight alkaline reaction 

Uses: 

• Antidote for cyanide poisoning 

• Used in volumetric analysis (iodometry) 

• Acts as antioxidant 

• Employed in photography as a fixer 

• Used in treating iodine poisoning 

 

8. Write short notes on acidifying and alkalinising agents. 

Acidifying Agents: 
These are substances that increase the acidity or lower the pH of a solution. 

Examples: 

• Dilute hydrochloric acid 

• Ammonium chloride 

Uses: 

• Aid digestion 

• Used to treat alkalosis 

• Help in urinary acidification 

Alkalinising Agents: 
Substances that increase the pH or reduce acidity. 

Examples: 

• Sodium bicarbonate 

• Potassium citrate 

Uses: 

• Treat acidosis 

• Manage urinary tract infections 

• Act as antacids 

9. What are the sources and types of impurities in pharmaceutical substances? 

Sources of Impurities: 

1. Raw materials: Impurities may be present in starting materials like salts or reagents. 

2. Manufacturing process: Use of catalysts, solvents, or reaction conditions may leave residual materials. 

3. Storage conditions: Exposure to light, moisture, or temperature may lead to degradation. 

4. Cross-contamination: May occur in multi-product facilities. 

5. Packaging materials: Interaction between the drug and container may add impurities. 

Types of Impurities: 

1. Organic impurities: 

1. From synthesis, starting materials, by-products. 

2. E.g., residual solvents, degradation products. 

2. Inorganic impurities: 

1. From reagents, catalysts, filter aids. 

2. E.g., heavy metals, sulphated ash. 

3. Residual solvents: 

1. Solvents used in synthesis not completely removed. 

2. E.g., methanol, dichloromethane. 

4. Environmental contaminants: 

1. Dust, microbes, or contamination from handling. 

Control Measures: 

• Use of Good Manufacturing Practices (GMP) 

• Limit tests (for chloride, sulphate, iron, etc.) 

• Validation and regular monitoring 

 

10. Define and classify antacids with suitable examples. 

Definition: 
Antacids are substances used to neutralize gastric acid in the stomach, providing relief from hyperacidity, heartburn, and indigestion. 

Classification: 

1. Systemic Antacids: 

1. Absorbed into systemic circulation. 

2. Fast but may cause systemic alkalosis. 

3. Example: Sodium bicarbonate 

2. Non-Systemic Antacids: 

1. Act locally in the stomach, not absorbed. 

2. Fewer systemic side effects. 

3. Subtypes: 

1. Aluminium-based: Aluminium hydroxide 

2. Magnesium-based: Magnesium hydroxide, magnesium trisilicate 

3. Calcium-based: Calcium carbonate 

4. Combination antacids: To balance constipating and laxative effects 

Examples: 

• Sodium bicarbonate (NaHCO₃) – Systemic 

• Aluminium hydroxide [Al(OH)₃] – Non-systemic 

• Magnesium hydroxide [Mg(OH)₂] 

• Calcium carbonate (CaCO₃) 

Use: 

• Treat gastric hyperacidity, peptic ulcers, acid reflux. 

 

11. Write the assay principle and procedure for ferrous sulphate. 

Principle: 
Ferrous sulphate is assayed by redox titration using potassium permanganate in an acidic medium. KMnO₄ oxidizes Fe²⁺ to Fe³⁺. 

Reaction: 
5Fe²⁺ + MnO₄⁻ + 8H⁺ → 5Fe³⁺ + Mn²⁺ + 4H₂O 

Procedure: 

1. Dissolve weighed quantity of ferrous sulphate in dilute sulphuric acid. 

2. Titrate with standard KMnO₄ solution until pink color persists. 

3. Each mL of 0.1 N KMnO₄ = 0.0278 g of FeSO₄ 

Endpoint: 
Appearance of permanent pale pink color. 

Precautions: 

• Use freshly prepared solution to avoid oxidation by air. 

• Ensure acidic medium with dilute H₂SO₄. 

 

12. What are buffering agents? Give properties and uses. 

Definition: 
Buffering agents are substances that help maintain a constant pH when small amounts of acid or base are added. 

Properties: 

• Composed of a weak acid and its salt (acidic buffer) or weak base and its salt (basic buffer). 

• Resist pH change within a narrow range. 

• Should be chemically stable and non-toxic. 

Common Buffer Systems: 

• Acetate buffer: Acetic acid + Sodium acetate 

• Phosphate buffer: H₂PO₄⁻ / HPO₄²⁻ 

• Borate buffer: Boric acid + Sodium borate 

Uses: 

• Maintain pH in parenteral, ophthalmic, and oral preparations 

• Used in biological systems to simulate physiological pH 

• Essential for enzyme activity and drug stability 

13. Write the preparation, properties and uses of hydrogen peroxide. 

Preparation: 

1. Laboratory method: 
   By hydrolysis of barium peroxide with dilute H₂SO₄: 
   BaO₂ + H₂SO₄ → BaSO₄↓ + H₂O₂ 

2. Commercial method: 
   Anthraquinone oxidation-reduction method. 

Properties: 

• Colorless, odorless liquid with a bitter taste 

• Slightly more viscous than water 

• Miscible with water in all proportions 

• Strong oxidizing and mild reducing agent 

• Unstable; decomposes to water and oxygen 
  2H₂O₂ → 2H₂O + O₂↑ (exothermic reaction) 

Storage: 
Stored in dark, airtight containers with stabilizers like acetanilide to prevent decomposition. 

Uses: 

• As antiseptic (mild disinfectant in 3% solution) 

• In bleaching (hair, textiles, paper) 

• In tooth whitening agents 

• Used in preparation of disinfectants 

• In analytical chemistry as oxidizing agent 

 

14. Explain the limit test for chloride. 

Principle: 
Chloride ions in the sample react with silver nitrate in the presence of nitric acid to form a white precipitate of silver chloride, which is compared with a standard. 

Reaction: 
Ag⁺ + Cl⁻ → AgCl↓ (white ppt) 

Procedure: 

1. Dissolve the sample in water in Nessler's cylinder. 

2. Add 1 mL of dilute nitric acid. 

3. Add 1 mL of silver nitrate solution. 

4. Mix and allow to stand for 5 minutes. 

5. Compare the opalescence with a standard chloride solution prepared similarly. 

Interpretation: 
If the turbidity (opalescence) in the test solution is not greater than that of the standard, the sample passes the test. 

Precautions: 

• Use freshly prepared solutions. 

• Avoid contamination. 

• Carry out the test in a dust-free environment. 

 

15. What are cathartics? Give classification and examples. 

Definition: 
Cathartics are drugs that accelerate defecation by increasing intestinal motility or water content in the bowel. 

Classification: 

1. Bulk-forming cathartics: 
   Increase stool bulk by absorbing water. 

1. Example: Methylcellulose, Psyllium husk 

2. Lubricant cathartics: 
   Soften stool by coating fecal matter. 

1. Example: Liquid paraffin 

3. Stimulant (irritant) cathartics: 
   Stimulate bowel mucosa and increase motility. 

1. Example: Senna, Castor oil 

4. Saline cathartics (osmotic): 
   Draw water into intestine via osmosis. 

1. Example: Magnesium sulphate, Sodium phosphate 

Uses: 

• Relieve constipation 

• Bowel clearance before surgery or radiological exams 

• Prevent straining in cardiac patients 

 

16. Write a note on official compounds of iron. 

Iron Compounds in IP (Indian Pharmacopoeia): 

1. Ferrous sulphate (FeSO₄·7H₂O): 

1. Pale green crystals 

2. Used in iron-deficiency anemia 

3. Assayed by redox titration with KMnO₄ 

2. Ferric ammonium citrate: 

1. Soluble in water, used as a hematinic 

2. Mild astringent and nutrient 

3. Ferric chloride (FeCl₃): 

1. Used as astringent and antiseptic 

2. Also used in water purification 

4. Ferrous fumarate and Ferrous gluconate: 

1. Better tolerated iron salts 

2. Oral iron supplements 

Uses of Official Iron Compounds: 

• Treat iron-deficiency anemia 

• Nutritional supplements 

• Astringent and antiseptic in topical formulations 

17. Define and classify acidifiers. 

Definition: 
Acidifiers are agents used to increase the acidity (lower the pH) of a solution, either systemically or locally. They are important in pharmaceutical formulations and for correcting systemic alkalosis. 

Classification: 

1. Systemic Acidifiers: 

1. Administered orally or parenterally to restore acidic pH of blood in systemic alkalosis. 

2. Example: Ammonium chloride 

2. Urinary Acidifiers: 

1. Used to acidify urine and treat urinary tract infections (UTIs). 

2. Example: Ascorbic acid 

3. Gastric Acidifiers: 

1. Replace or supplement hydrochloric acid in the stomach in achlorhydria. 

2. Example: Dilute HCl, Glutamic acid HCl 

Examples: 

• Ammonium chloride (NH₄Cl) – systemic acidifier 

• Ascorbic acid (Vitamin C) – urinary acidifier 

• Dilute HCl – gastric acidifier 

Uses: 

• Correct metabolic alkalosis 

• Maintain acidity in urine 

• Aid in digestion by supplementing gastric acid 

 

18. Write the preparation and assay of potassium iodide. 

Preparation: 

1. From Iodine and Potassium Hydroxide: 

I₂ + 6KOH → 5KI + KIO₃ + 3H₂O 
(Then, iodate is reduced to iodide by heating with charcoal) 

2. From HI and K₂CO₃: 

2HI + K₂CO₃ → 2KI + H₂O + CO₂ 

Assay: 

Principle: 
Titration with potassium iodate (KIO₃). Iodate reacts with iodide in acidic medium to liberate iodine, which is titrated with sodium thiosulphate using starch as an indicator. 

Reaction: 

IO₃⁻ + 5I⁻ + 6H⁺ → 3I₂ + 3H₂O 
I₂ + 2Na₂S₂O₃ → 2NaI + Na₂S₄O₆ 

Procedure: 

1. Weigh and dissolve sample in water. 

2. Add dilute sulphuric acid and excess potassium iodate. 

3. Titrate liberated iodine with 0.1 N sodium thiosulphate. 

4. Use starch as an indicator near the endpoint. 

Endpoint: 
Disappearance of blue color. 

 

19. Discuss the role of electrolyte in the body with examples. 

Definition: 
Electrolytes are substances that dissociate into ions in body fluids and are essential for various physiological functions. 

Major Electrolytes: 

• Sodium (Na⁺): Regulates extracellular fluid volume, nerve impulses 

• Potassium (K⁺): Maintains intracellular fluid, muscle contraction 

• Calcium (Ca²⁺): Muscle function, nerve signaling, blood clotting 

• Chloride (Cl⁻): Maintains osmotic balance, acid-base balance 

• Bicarbonate (HCO₃⁻): Buffers blood pH 

Roles in the Body: 

1. Fluid Balance: 

1. Maintain osmotic pressure and water distribution. 

2. Nerve and Muscle Function: 

1. Na⁺ and K⁺ essential for action potential and muscle contraction. 

3. Acid-Base Balance: 

1. Bicarbonate and phosphate ions help maintain blood pH. 

4. Enzyme Activation: 

1. Mg²⁺ and Ca²⁺ act as cofactors. 

5. Heart Function: 

1. K⁺ and Ca²⁺ regulate heartbeat and rhythm. 

Examples in Therapy: 

• ORS (Oral Rehydration Salts): Restore electrolytes in dehydration 

• Electrolyte infusions: For electrolyte imbalances 

 

20. Explain the principle and procedure of limit test for heavy metals. 

Principle: 
Heavy metals like Pb, Hg, and As are detected by their reaction with hydrogen sulfide (H₂S) in acidic medium, forming colored sulfide precipitates. The intensity of the color is compared with a standard. 

Procedure: 

1. Dissolve the sample in water and adjust pH using buffer solution. 

2. Pass H₂S gas through the solution for 1–2 minutes. 

3. Let it stand for 5 minutes. 

4. Compare the color of the precipitate formed with that of a standard lead solution. 

Standard Used: 
Standard solution contains a known quantity of lead (e.g., 20 ppm Pb). 

Reaction: 
Pb²⁺ + H₂S → PbS (black precipitate) 

Interpretation: 
If the color of the test solution is not darker than the standard, it passes the test. 

21. What are protective and adsorbents? Give examples. 

Protectives: 

• These are substances that form a protective coating over the mucosal lining of the gastrointestinal tract to protect it from irritants. 

• They are used in the treatment of gastritis, ulcers, and other GI irritations. 

Examples of Protectives: 

1. Bismuth subcarbonate 

2. Zinc oxide 

3. Kaolin 

Mechanism: 

• They coat the mucosa and prevent contact with irritants or gastric acid. 

 

Adsorbents: 

• Adsorbents are substances that adsorb gases, toxins, and bacteria from the GI tract. 

• They are commonly used in the treatment of poisoning, diarrhea, and indigestion. 

Examples of Adsorbents: 

1. Activated charcoal – used in poisoning cases 

2. Kaolin – used as an antidiarrheal agent 

3. Magnesium trisilicate 

Mechanism: 

• Adsorb toxins on their surface, preventing their absorption in the intestines. 

Uses: 

• Used in diarrhea, food poisoning, flatulence, and other GI disturbances. 

• Commonly included in formulations for upset stomach or food poisoning. 

 

22. Write a short note on dental products. 

Dental products are pharmaceutical formulations used for oral hygiene, treatment, and prevention of dental conditions like caries, plaque, gingivitis, and bad breath. 

Types of Dental Products: 

1. Toothpaste: 

1. Contains abrasives, fluoride (for anti-caries), sweeteners, and surfactants. 

2. Example: Fluoridated toothpaste (sodium fluoride) 

2. Mouthwashes: 

1. Used for oral disinfection and fresh breath. 

2. May contain chlorhexidine, hydrogen peroxide, or alcohol. 

3. Tooth powders: 

1. Similar to toothpaste but in powder form. 

2. Contain mild abrasives like calcium carbonate. 

4. Anti-caries agents: 

1. Sodium fluoride and stannous fluoride help strengthen enamel and prevent dental caries. 

5. Whitening agents: 

1. Contain hydrogen peroxide or baking soda (sodium bicarbonate). 

Uses: 

• Remove food debris and plaque 

• Prevent cavities and dental diseases 

• Maintain oral hygiene and fresh breath 

• Treat gum-related conditions 

 

23. Describe various pharmaceutical aids. 

Definition: 
Pharmaceutical aids are substances that have little or no pharmacological effect themselves but are used in the preparation and preservation of pharmaceutical formulations. 

Types and Examples: 

1. Solvents: 

1. Used to dissolve drugs or aid in formulation. 

2. Examples: Water, ethanol, glycerin 

2. Coloring agents: 

1. Used to enhance the appearance of drugs. 

2. Examples: Tartrazine, erythrosine 

3. Preservatives: 

1. Prevent microbial contamination. 

2. Examples: Benzalkonium chloride, parabens 

4. Flavouring agents: 

1. Improve taste and palatability. 

2. Examples: Vanilla, orange oil 

5. Sweeteners: 

1. Enhance the taste of oral preparations. 

2. Examples: Sucrose, saccharin, aspartame 

6. Binders and Disintegrants: 

1. Improve tablet formulation and drug release. 

2. Examples: Starch, cellulose derivatives 

Importance: 

• Improve stability, appearance, and palatability of drugs 

• Facilitate drug delivery and patient compliance 

• Ensure effectiveness and safety of dosage forms 

 

24. Discuss the role and applications of sodium nitrite. 

Role: 

Sodium nitrite (NaNO₂) acts as an antidote, preservative, and vasodilator in pharmaceutical and clinical use. 

Applications: 

1. Antidote in Cyanide Poisoning: 

1. Converts hemoglobin to methemoglobin, which binds cyanide, preventing it from affecting cytochrome enzymes. 

2. Administered intravenously in emergency settings. 

2. Vasodilator: 

1. Used occasionally to treat angina pectoris and high blood pressure. 

2. Relaxes smooth muscles and dilates blood vessels. 

3. Preservative: 

1. Prevents bacterial growth in processed foods, especially in meat products (also has pharmaceutical relevance). 

4. Diagnostic Use: 

1. In radiopharmaceuticals and chemical assays. 

5. Other uses: 

1. Sometimes used in the preparation of diazotization reactions in lab settings. 

Precautions: 

• Toxic in high doses – may cause methemoglobinemia 

• Should be used under medical supervision 

25. Write preparation, properties and uses of sodium thiosulphate. 

Preparation: 

• Sodium thiosulphate (Na₂S₂O₃·5H₂O) is prepared by heating a solution of sodium sulphite with sulphur: 

Na₂SO₃ + S → Na₂S₂O₃ 

• The solution is then crystallized to obtain pentahydrate crystals. 

 

Properties: 

• White, crystalline powder 

• Odorless and soluble in water, insoluble in alcohol 

• Stable in dry air but decomposes in moist air 

• Melts and loses water of crystallization on heating 

• Slightly alkaline to litmus 

 

Uses: 

1. Antidote in Cyanide Poisoning: 

1. Reacts with cyanide to form non-toxic thiocyanate. 

CN⁻ + S₂O₃²⁻ → SCN⁻ + SO₃²⁻ 

2. Iodometry: 

1. Used as a titrant in volumetric analysis involving iodine. 

3. Photography: 

1. Acts as a fixing agent by removing unreacted silver halides. 

4. Fungicide and Disinfectant: 

1. Used in surface sterilization and for skin infections. 

5. Chlorine Neutralizer: 

1. Removes excess chlorine in water treatment. 

 

26. What are antacids? Classify them with examples. 

Definition: 

Antacids are substances that neutralize excess gastric acid in the stomach, relieving symptoms of hyperacidity, gastritis, and peptic ulcers. 

 

Classification: 

1. Systemic Antacids (absorbable): 

• Soluble in water and absorbed into circulation 

• Can cause systemic alkalosis 

Examples: Sodium bicarbonate, sodium citrate 

 

2. Non-Systemic Antacids (non-absorbable): 

• Insoluble, not absorbed 

• Act locally and do not disturb systemic acid-base balance 

Examples: 

• Magnesium hydroxide (laxative effect) 

• Aluminium hydroxide (constipating effect) 

• Magnesium trisilicate 

• Calcium carbonate 

 

Ideal Properties of Antacids: 

• Quick action 

• Prolonged buffering effect 

• Non-toxic 

• Does not cause acid rebound or systemic alkalosis 

 

Combination Therapy: 

To balance constipating and laxative effects, mixtures like magnesium hydroxide and aluminium hydroxide are used. 

 

27. Define and classify cathartics. Give uses. 

Definition: 

Cathartics (also known as purgatives or laxatives) are substances that accelerate defecation by promoting bowel movements. They help relieve constipation. 

 

Classification: 

1. Bulk-forming Cathartics: 

1. Absorb water and swell, increasing bulk 

2. Example: Psyllium husk 

2. Osmotic (Saline) Cathartics: 

1. Draw water into intestines via osmosis 

2. Examples: Magnesium sulphate, sodium phosphate 

3. Stimulant Cathartics: 

1. Stimulate intestinal peristalsis 

2. Examples: Senna, castor oil 

4. Emollient (Lubricant) Cathartics: 

1. Soften stool by lubricating bowel 

2. Examples: Liquid paraffin 

 

Uses: 

• Relief from constipation 

• Bowel cleansing before surgery or radiological procedures 

• Elimination of toxins and poisons 

• In patients with hemorrhoids or after rectal surgery (soft stools reduce strain) 

28. Describe the principle and procedure of limit test for chlorides. 

Principle: 

The limit test for chlorides is based on the reaction of chloride ions with silver nitrate (AgNO₃) in the presence of dilute nitric acid (HNO₃) to form silver chloride (AgCl), a white turbidity. The intensity of turbidity is compared with a standard solution to determine whether the chloride content is within permissible limits. 

Chemical Reaction: 

Cl⁻ + Ag⁺ → AgCl↓ (white turbidity) 

 

Procedure: 

1. Test Sample Preparation: 

• Dissolve a specified quantity of the test substance in distilled water. 

• Add 1 mL of dilute nitric acid. 

• Make up the volume to 50 mL with distilled water in a Nessler’s cylinder. 

• Add 1 mL of 0.1 M silver nitrate solution. 

• Stir and allow to stand for 5 minutes. 

2. Standard Preparation: 

• Prepare standard chloride solution using 1 mL of 0.05845% w/v sodium chloride solution (equivalent to 1 mg of Cl⁻). 

• Add 1 mL of dilute nitric acid and dilute to 50 mL with distilled water. 

• Add 1 mL of silver nitrate solution and proceed similarly. 

3. Observation: 

• Compare the turbidity of the test solution with the standard. 

• The turbidity in the test solution should not be more intense than the standard. 

 

Importance: 

• Ensures the pharmaceutical substance complies with IP/USP limits. 

• Chloride contamination may originate from raw materials or manufacturing processes and needs to be monitored. 

 

29. Write short note on pharmaceutical aids. 

Definition: 

Pharmaceutical aids are substances that are not active drugs but are used in the formulation, manufacture, and preservation of pharmaceutical products. 

 

Types and Examples: 

1. Solvents: 

1. Dissolve active ingredients or aid formulation. 

2. Example: Water, ethanol, glycerin 

2. Coloring Agents: 

1. Provide visual appeal and identity. 

2. Example: Tartrazine, erythrosine 

3. Preservatives: 

1. Inhibit microbial growth and increase shelf-life. 

2. Example: Methyl paraben, benzalkonium chloride 

4. Flavouring Agents: 

1. Mask unpleasant taste. 

2. Example: Peppermint oil, orange flavor 

5. Sweeteners: 

1. Improve taste in oral formulations. 

2. Example: Sucrose, saccharin 

6. Binders and Disintegrants: 

1. Help tablet formation and drug release. 

2. Example: Starch, microcrystalline cellulose 

 

Importance: 

• Enhance product acceptability and effectiveness. 

• Improve taste, appearance, and stability. 

• Essential in modern pharmaceutical formulation. 

30. Explain the assay of hydrogen peroxide. 

Assay Method: 
Hydrogen peroxide (H₂O₂) is assayed by redox titration using potassium permanganate (KMnO₄) as the titrant in the presence of dilute sulfuric acid. It is based on the oxidation of H₂O₂. 

 

Principle: 

Hydrogen peroxide acts as a reducing agent and reacts with potassium permanganate in acidic medium. KMnO₄ is a strong oxidizing agent and oxidizes H₂O₂ to oxygen gas, while itself getting reduced to Mn²⁺. 

Reaction: 

2 KMnO₄ + 5 H₂O₂ + 3 H₂SO₄ → K₂SO₄ + 2 MnSO₄ + 5 O₂ ↑ + 8 H₂O 

 

Procedure: 

1. Take an accurately measured quantity of hydrogen peroxide solution in a flask. 

2. Add dilute sulfuric acid to make the medium acidic. 

3. Titrate with standardized 0.1 N potassium permanganate solution. 

4. The endpoint is the appearance of a persistent pale pink color. 

 

Calculation: 

1 mL of 0.1 N KMnO₄ ≡ 1.701 mg of H₂O₂ 

Using this, the amount of hydrogen peroxide in the solution can be calculated. 

 

Significance: 

• Ensures the strength and purity of H₂O₂ in pharmaceutical preparations. 

• Required for antiseptic and disinfectant applications. 

• Concentrated H₂O₂ can decompose or lose potency over time; hence assay ensures stability and safety. 

 

31. What are dental products? Write a note on their pharmaceutical use. 

Definition: 

Dental products are pharmaceutical preparations used for the prevention, treatment, and maintenance of dental health. They include pastes, powders, rinses, and antiseptics. 

 

Types and Examples: 

1. Dentifrices (Toothpastes & Powders): 

1. Contain abrasives (calcium carbonate), humectants (glycerin), sweeteners, and fluoride. 

2. Help in cleaning teeth and preventing plaque. 

2. Fluoride Compounds: 

1. Example: Sodium fluoride, stannous fluoride 

2. Strengthen tooth enamel and prevent dental caries. 

3. Antiseptic Mouthwashes: 

1. Contain chlorhexidine or povidone iodine. 

2. Used for oral hygiene and in conditions like gingivitis. 

4. Desensitizing Agents: 

1. Example: Potassium nitrate 

2. Reduce tooth sensitivity by blocking nerve response. 

 

Pharmaceutical Use: 

• Prevent dental plaque and tartar. 

• Maintain oral hygiene and fresh breath. 

• Prevent and treat tooth decay and gum diseases. 

• Used post-dental procedures for disinfection and healing. 

32. Write note on role of electrolytes in body fluids. 

Definition: 

Electrolytes are substances that dissociate into ions in body fluids and are essential for numerous physiological functions. Common electrolytes include sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl⁻), bicarbonate (HCO₃⁻), and phosphate (PO₄³⁻). 

 

Role in Body Fluids: 

1. Maintain Osmotic Balance: 

1. Electrolytes regulate osmotic pressure and fluid distribution between intracellular fluid (ICF) and extracellular fluid (ECF). 

2. Sodium is the main ECF ion; potassium is dominant in ICF. 

2. Acid-Base Balance: 

1. Bicarbonate and phosphate ions act as buffers, maintaining the blood’s pH. 

3. Nerve Impulse Transmission: 

1. Sodium and potassium ions are involved in action potential generation and nerve impulse conduction. 

4. Muscle Function: 

1. Calcium and magnesium are essential for muscle contraction and relaxation. 

5. Enzyme Activation: 

1. Electrolytes like Mg²⁺ act as cofactors for various enzymatic reactions. 

6. Water Balance and Hydration: 

1. Proper electrolyte concentration is essential to prevent dehydration or overhydration. 

 

Imbalances and Effects: 

• Hyponatremia: Low sodium → confusion, seizures. 

• Hyperkalemia: High potassium → cardiac arrhythmia. 

• Hypocalcemia: Low calcium → muscle cramps, spasms. 

 

Conclusion: 

Electrolytes are vital for physiological homeostasis. Electrolyte replenishment (e.g., via ORS) is critical during fluid loss due to diarrhea, vomiting, or excessive sweating. 

 

33. Write a note on various sources of impurities. 

Impurities in pharmaceutical substances can arise from various sources during manufacturing, storage, or handling. These impurities may affect drug safety, efficacy, and stability. 

 

Sources of Impurities: 

1. Raw Materials: 

1. Impure starting materials or reagents may introduce contaminants. 

2. Example: Arsenic from phosphate rocks. 

2. Manufacturing Process: 

1. Incomplete reactions, side reactions, and residual solvents. 

2. Mechanical contamination from machinery (iron, grease). 

3. Storage Conditions: 

1. Interaction with container material (glass leaching lead). 

2. Degradation due to temperature, light, or humidity. 

4. Cross-contamination: 

1. During multi-product manufacturing in shared facilities. 

5. Chemical Instability: 

1. Hydrolysis, oxidation, or photodegradation of compounds. 

2. Example: Hydrogen peroxide decomposing to water and oxygen. 

6. Environmental Contaminants: 

1. Dust, microorganisms, or heavy metals from the environment. 

 

Conclusion: 

Identification and control of impurities are essential for ensuring drug quality and patient safety. Limit tests and GMP practices help minimize impurity levels in pharmaceutical preparations. 

34. Write the preparation and assay of sodium nitrite. 

Preparation: 

Sodium nitrite (NaNO₂) is prepared industrially by: 

1. Absorption of Nitric Oxide (NO): 

1. Nitric oxide is oxidized to nitrogen dioxide (NO₂), which is then absorbed in a sodium carbonate or sodium hydroxide solution. 

2 NO₂ + Na₂CO₃ → 2 NaNO₂ + CO₂ 

2. Alternative Lab Method: 

1. Nitrous acid (HNO₂) can be neutralized with sodium hydroxide: 
   HNO₂ + NaOH → NaNO₂ + H₂O 

 

Assay: 

The assay is carried out by iodometric titration. 

Principle: 
Sodium nitrite reacts with potassium iodide (KI) in acidic medium to liberate iodine (I₂). The liberated iodine is titrated with standard sodium thiosulphate solution using starch as an indicator. 

Chemical Reaction: 

2 NaNO₂ + 2 KI + 2 H₂SO₄ → 2 I₂ + 2 NaHSO₄ + 2 H₂O 
I₂ + 2 Na₂S₂O₃ → 2 NaI + Na₂S₄O₆ 

 

Procedure: 

1. Dissolve a known quantity of sodium nitrite in water. 

2. Add excess KI and dilute sulfuric acid. 

3. Titrate the liberated iodine with 0.1 N sodium thiosulphate. 

4. Use starch as the indicator; endpoint is disappearance of blue color. 

 

Calculation: 

1 mL of 0.1 N Na₂S₂O₃ ≡ 3.45 mg of NaNO₂ 

 

Conclusion: 

This assay ensures the purity and correct dosage of sodium nitrite, which is used as a vasodilator, preservative, and antidote in cyanide poisoning. 

 

35. Define and classify acidifiers. Give examples. 

Definition: 

Acidifiers are substances that increase the acidity of a solution or the body fluids. In pharmacy, they are used to maintain acidic pH, assist digestion, or act as systemic/urinary acidifiers. 

 

Classification: 

1. Systemic Acidifiers: 

1. Lower the pH of blood and body fluids. 

2. Examples: Ammonium chloride, dilute hydrochloric acid 

2. Urinary Acidifiers: 

1. Acidify urine to treat infections or aid drug solubility. 

2. Examples: Ascorbic acid, ammonium chloride 

3. Gastric Acidifiers: 

1. Supplement low stomach acid levels (hypochlorhydria). 

2. Examples: Dilute HCl, citric acid 

 

Uses: 

• Treat metabolic alkalosis 

• Aid digestion 

• Increase solubility and excretion of weak bases 

• Maintain acidic urine to prevent bacterial growth 

 

Conclusion: 

Acidifiers play a key role in therapeutic and formulation aspects. The proper selection depends on the site of action—gastric, systemic, or urinary. 

36. Write short note on protective and adsorbents. 

Definition: 

• Protectives are agents that form a protective coating on inflamed or injured mucous membranes to prevent irritation. 

• Adsorbents are substances that bind to toxins, gases, or irritants on the mucosal surface and prevent their absorption or activity. 

 

Protectives: 

• Act by coating the mucosal surface and shielding it from irritants. 

• Often used in gastrointestinal and dermatological preparations. 

Examples: 

• Zinc oxide: Used in calamine lotion and ointments for skin protection. 

• Calamine: Soothes itching and minor skin irritations. 

• Bismuth subcarbonate: Used in antacid formulations. 

 

Adsorbents: 

• Adsorb (not absorb) toxins or gases onto their surface through physical binding, thus neutralizing their harmful effects. 

• Commonly used in diarrhea, flatulence, and poisoning. 

Examples: 

• Activated charcoal: Used in poisoning due to its large surface area. 

• Kaolin: Used in anti-diarrheal formulations. 

• Magnesium trisilicate: Has both adsorbent and antacid actions. 

 

Uses in Pharmacy: 

• To protect mucosal linings from chemical or microbial irritation. 

• In the management of diarrhea and gastrointestinal discomfort. 

• As topical agents for minor cuts, burns, and rashes. 

 

Conclusion: 

Protectives and adsorbents are vital pharmaceutical aids. Their non-systemic, localized action makes them safe and effective in a variety of conditions. 

 

37. Explain the limit test for sulphate. 

Purpose: 

The limit test for sulphate is performed to detect and control the amount of sulphate (SO₄²⁻) impurities in pharmaceutical substances. 

 

Principle: 

Sulphate ions react with barium chloride in the presence of dilute hydrochloric acid to form a white barium sulphate precipitate. The turbidity produced is compared with a standard solution. 

Chemical Reaction: 

BaCl₂ + Na₂SO₄ → BaSO₄ ↓ + 2 NaCl 

 

Procedure: 

1. Dissolve the test sample in water and add 1 mL of dilute HCl. 

2. Add 1 mL of barium chloride solution. 

3. Mix and allow to stand for 5 minutes. 

4. Compare the turbidity with a standard sulphate solution prepared in the same way. 

 

Interpretation: 

• If the turbidity of the test solution is not greater than that of the standard, it passes the test. 

• Indicates that sulphate impurity is within the permissible limit. 

 

Importance: 

• Sulphates may come from water, reagents, or containers. 

• Excess sulphate may alter drug stability or react with other components. 

 

Conclusion: 

Limit tests are crucial for quality control. The sulphate limit test ensures pharmaceutical substances are free from harmful levels of sulphate impurities. 

38. Write properties and uses of hydrogen peroxide. 

Chemical Formula: H₂O₂ 
Molecular Weight: 34.01 g/mol 

 

Properties: 

1. Appearance: 

1. Colorless, transparent liquid with a bitter taste. 

2. Stability: 

1. Unstable; decomposes slowly on exposure to light or heat into water and oxygen: 
   2 H₂O₂ → 2 H₂O + O₂ ↑ 

2. Stabilized with substances like acetanilide. 

3. Solubility: 

1. Miscible with water in all proportions. 

4. Oxidizing Property: 

1. Acts as a strong oxidizing agent in acidic and basic media. 

5. Decomposition: 

1. Catalyzed by light, heat, metals, and enzymes like catalase. 

6. Concentration: 

1. Used typically in 3% solution (10 volumes) for pharmaceutical use. 

 

Uses: 

1. Antiseptic: 

1. 3% solution used for cleansing wounds, mouthwash, and treating oral infections. 

2. Disinfectant: 

1. Used for sterilizing surfaces and instruments in hospitals. 

3. Oxidizing Agent: 

1. Employed in the manufacture of chemicals and pharmaceuticals. 

4. Bleaching Agent: 

1. Used in hair bleach and for delicate materials like wool and silk. 

5. Tooth Whitening: 

1. Used in low concentrations in dental preparations. 

6. Analytical Reagent: 

1. Used in redox titrations. 

 

Storage: 

• Stored in well-closed, light-resistant containers in a cool place to prevent decomposition. 

 

Conclusion: 
Hydrogen peroxide is a versatile pharmaceutical agent with powerful oxidizing and antiseptic properties. Its wide use in medicine, industry, and labs makes it essential in the pharmacopeia. 

 

39. Define and classify antacids with examples. 

Definition: 
Antacids are substances that neutralize excess gastric acid (HCl) in the stomach and provide relief from acidity, heartburn, and indigestion. 

 

Classification: 

1. Systemic Antacids: 

1. Absorbed into the bloodstream. 

2. Rapid action but may cause systemic alkalosis. 

3. Example: Sodium bicarbonate 

2. Non-Systemic Antacids: 

1. Not absorbed systemically; act locally in the stomach. 

2. Subtypes: 

1. Aluminum salts: Slow acting, constipating 
   Example: Aluminum hydroxide 

2. Magnesium salts: Rapid acting, laxative effect 
   Example: Magnesium hydroxide 

3. Calcium salts: May cause rebound hyperacidity 
   Example: Calcium carbonate 

3. Combined Antacids: 

1. Combination of aluminum and magnesium salts to balance side effects. 

2. Example: Gelusil (Al(OH)₃ + Mg(OH)₂) 

 

Ideal Properties: 

• Should not cause systemic alkalosis 

• Rapid onset with prolonged action 

• Should not interfere with digestion or electrolyte balance 

 

Conclusion: 
Antacids are essential OTC drugs for acid-related disorders. Proper formulation ensures effectiveness and minimizes side effects. 

40. Write a note on pharmaceutical buffers. 

Definition: 

Pharmaceutical buffers are solutions that resist changes in pH when small amounts of acid or base are added. They are used to maintain a stable pH in pharmaceutical formulations for optimal drug stability and effectiveness. 

 

Types of Buffers: 

1. Acidic Buffers: 

1. Contain a weak acid and its conjugate base (salt). 

2. Example: Acetic acid + sodium acetate 

2. Basic Buffers: 

1. Contain a weak base and its conjugate acid. 

2. Example: Ammonium hydroxide + ammonium chloride 

 

Common Pharmaceutical Buffers: 

• Phosphate Buffer: pH range 6.0–8.0 

• Citrate Buffer: pH range 3.0–6.2 

• Acetate Buffer: pH range 3.6–5.6 

• Borate Buffer: pH range 8.0–10.0 

 

Applications in Pharmacy: 

1. Stability: 

1. Helps maintain the stability of drugs sensitive to pH changes. 

2. Solubility: 

1. Many drugs are more soluble or stable at specific pH values. 

3. Isotonicity and Compatibility: 

1. Buffers help prevent irritation when applied to eyes or injected. 

4. Biological Compatibility: 

1. Maintains pH similar to body fluids (e.g., eye drops, injections). 

 

Ideal Properties: 

• Should not be toxic or interfere with the drug. 

• Should be stable and maintain pH throughout shelf life. 

• Should be compatible with all formulation components. 

 

Conclusion: 

Pharmaceutical buffers are essential components in formulations. They ensure product efficacy, stability, and patient safety by maintaining the required pH. 

 

41. Define impurities. Classify and explain their sources. 

Definition: 

Impurities are unwanted chemical substances present in pharmaceutical substances that affect purity, safety, and therapeutic efficacy. 

 

Classification of Impurities: 

1. Organic Impurities: 

1. By-products, starting materials, degradation products. 

2. Inorganic Impurities: 

1. Reagents, catalysts, salts, heavy metals. 

3. Residual Solvents: 

1. Organic solvents used in synthesis or purification. 

4. Physical Impurities: 

1. Dust, glass, fibers, or environmental contaminants. 

 

Sources of Impurities: 

1. Raw Materials: 

1. Impure chemicals or water used in manufacturing. 

2. Manufacturing Process: 

1. Incomplete reactions, contamination during mixing or handling. 

3. Storage Conditions: 

1. Light, temperature, and moisture may cause degradation. 

4. Packaging Materials: 

1. Leaching of chemicals from containers or closures. 

5. Cross-Contamination: 

1. Use of shared equipment without proper cleaning. 

 

Control Measures: 

• Follow Good Manufacturing Practices (GMP) 

• Use validated analytical methods (e.g., limit tests) 

• Store under appropriate temperature, humidity, and light conditions 

 

Conclusion: 

Impurities in pharmaceuticals must be carefully controlled. Their identification, classification, and elimination are crucial for product quality and patient safety. 

42. Write the preparation, assay and uses of potassium iodide. 

Chemical Formula: KI 
Molecular Weight: 166.0 g/mol 

 

Preparation: 

Potassium iodide is prepared by: 

1. Reacting iodine with potassium hydroxide (KOH): 

3I2+6KOH→5KI+KIO3+3H2O3I_2 + 6KOH \rightarrow 5KI + KIO_3 + 3H_2O3I2 +6KOH→5KI+KIO3 +3H2 O  

2. The resulting iodate (KIO₃) is reduced with charcoal to get more KI: 

KIO3+3C→KI+3COKIO_3 + 3C \rightarrow KI + 3COKIO3 +3C→KI+3CO  

3. The product is purified and crystallized. 

 

Assay: 

Principle: 

• The iodide ion (I⁻) is oxidized by potassium iodate (KIO₃) in acidic medium to liberate iodine, which is titrated with sodium thiosulphate. 

Reaction: 

IO3−+5I−+6H+→3I2+3H2OIO_3^- + 5I^- + 6H^+ \rightarrow 3I_2 + 3H_2O IO3− +5I−+6H+→3I2 +3H2 O I2+2Na2S2O3→2NaI+Na2S4O6I_2 + 2Na_2S_2O_3 \rightarrow 2NaI + Na_2S_4O_6I2 +2Na2 S2 O3 →2NaI+Na2 S4 O6   

Procedure: 

• Dissolve a known weight of KI in water. 

• Add dilute HCl and KIO₃. 

• Titrate the liberated iodine with standard sodium thiosulphate using starch as an indicator. 

 

Uses: 

1. Expectorant: Helps in liquefying mucus in respiratory conditions. 

2. Iodine Source: Provides iodide for thyroid hormone synthesis in goiter. 

3. Antifungal Agent: Used in sporotrichosis. 

4. Radiation Protection: Blocks radioactive iodine uptake in the thyroid. 

5. Component in Lugol’s Iodine: Used as antiseptic and in pre-thyroidectomy preparation. 

 

Conclusion: 
Potassium iodide is a vital pharmaceutical compound with diagnostic, therapeutic, and protective applications, especially in thyroid-related and respiratory conditions. 

 

43. What are cathartics? Give classification and uses. 

Definition: 
Cathartics are agents that accelerate defecation and are used to relieve constipation or evacuate the bowel before surgical or diagnostic procedures. 

 

Classification: 

1. Stimulant Cathartics (Irritant): 

1. Stimulate intestinal mucosa directly. 

2. Examples: Senna, Castor oil, Bisacodyl 

2. Bulk-forming Cathartics: 

1. Increase bulk of stool by absorbing water. 

2. Examples: Methylcellulose, Psyllium husk 

3. Lubricant Cathartics: 

1. Lubricate and soften stool. 

2. Example: Liquid paraffin 

4. Osmotic (Saline) Cathartics: 

1. Retain water in the intestines by osmosis. 

2. Examples: Magnesium sulphate, Sodium phosphate 

 

Uses: 

• Relieve constipation or bowel irregularity. 

• Prepare bowel for surgery or radiological procedures. 

• Expel toxins or parasites. 

• Used in cases of drug poisoning (with caution). 

 

Cautions: 

• Overuse can cause electrolyte imbalance or dependence. 

• Not suitable for patients with intestinal obstruction or inflammatory bowel diseases. 

 

Conclusion: 
Cathartics are essential agents in therapeutic and diagnostic settings, but they must be used judiciously to avoid complications. 

44. Explain the identification tests for anions. 

Identification of anions in pharmaceutical substances is essential to ensure the authenticity and quality of the compound. Common inorganic anions include chloride, sulfate, carbonate, nitrate, phosphate, and others. Specific reagents are used to detect each. 

 

1. Test for Chloride (Cl⁻): 

• Reagent: Silver nitrate (AgNO₃) 

• Procedure: To the solution, add dil. nitric acid followed by AgNO₃. 

• Observation: White curdy precipitate of AgCl, soluble in ammonium hydroxide. 

2. Test for Sulfate (SO₄²⁻): 

• Reagent: Barium chloride (BaCl₂) 

• Procedure: Add BaCl₂ to acidified solution. 

• Observation: White precipitate of barium sulfate, insoluble in HCl. 

3. Test for Carbonate (CO₃²⁻): 

• Reagent: Dilute HCl 

• Procedure: Add dilute HCl to the substance. 

• Observation: Effervescence due to CO₂ gas, which turns lime water milky. 

4. Test for Phosphate (PO₄³⁻): 

• Reagent: Ammonium molybdate solution 

• Procedure: Add ammonium molybdate to nitric acidified sample. 

• Observation: Yellow precipitate of ammonium phosphomolybdate. 

5. Test for Nitrate (NO₃⁻): 

• Reagent: Diphenylamine or brucine sulphate 

• Procedure: Add concentrated H₂SO₄ and reagent to nitrate solution. 

• Observation: Development of deep blue or red color indicates nitrate. 

 

Conclusion: 

Each anion has specific confirmatory tests based on its reaction with suitable reagents. These tests help in the identification and qualitative analysis of pharmaceutical substances to ensure compliance with pharmacopoeial standards. 

 

45. Describe pharmaceutical buffers with examples. 

Definition: 

Pharmaceutical buffers are solutions composed of a weak acid and its conjugate base (or a weak base and its conjugate acid), which resist changes in pH upon the addition of small amounts of acid or base. 

 

Types of Buffers: 

1. Acidic Buffers: 

1. Example: Acetic acid + sodium acetate (pH ~4.76) 

2. Basic Buffers: 

1. Example: Ammonium hydroxide + ammonium chloride (pH ~9) 

 

Examples Used in Pharmacy: 

• Phosphate Buffer: Sodium dihydrogen phosphate + disodium hydrogen phosphate (pH 6–8) 

• Citrate Buffer: Citric acid + sodium citrate (pH 3–6.2) 

• Borate Buffer: Boric acid + sodium borate (pH 8–10) 

 

Applications: 

• Formulation Stability: Maintains the pH for chemical stability. 

• Solubility Control: Helps in maintaining solubility of drugs. 

• Biocompatibility: Maintains pH close to physiological levels for ophthalmic and injectable preparations. 

• Analytical Use: Used in titrations and assays. 

 

Desirable Properties: 

• Should not be toxic or reactive. 

• Should maintain pH over the shelf life. 

• Compatible with active pharmaceutical ingredients (APIs). 

 

Conclusion: 

Buffers are crucial in pharmaceutical preparations to stabilize pH and ensure product safety, efficacy, and patient comfort. Their proper selection depends on the required pH range and compatibility with drug substances. 

46. Write short note on acidifying agents. 

Definition: 

Acidifying agents are substances used in pharmaceutical formulations to maintain or lower the pH of a solution or body fluids. They help in preserving the stability, solubility, and bioavailability of certain drugs. 

 

Types of Acidifying Agents: 

1. Systemic Acidifiers: Affect the body’s systemic pH. 

1. Example: Ammonium chloride 

2. Urinary Acidifiers: Acidify urine, altering drug excretion. 

1. Example: Ascorbic acid 

3. Local Acidifiers: Used in pharmaceutical formulations to maintain pH. 

1. Examples: Citric acid, Acetic acid 

 

Examples of Common Acidifying Agents: 

• Hydrochloric acid (HCl): Strong acid, used in preparations for pH control. 

• Citric acid: Used in effervescent tablets and syrups. 

• Boric acid: Mild acid, used in ophthalmic solutions. 

 

Uses: 

• Solubility Enhancement: Some drugs are more soluble in acidic medium. 

• Stability: Certain active pharmaceutical ingredients (APIs) degrade in alkaline conditions; acidifiers help prevent this. 

• Urinary pH Adjustment: Assists in treating urinary tract infections. 

• Taste Modification: Provides sour taste in syrups and chewables. 

• Preservative Effect: Lower pH inhibits microbial growth in some products. 

 

Conclusion: 

Acidifying agents are essential in both formulation development and therapeutic treatment. Their correct selection depends on the intended use—whether local (formulation) or systemic (therapeutic). 

 

47. Write a note on electrolyte replenisher. 

Definition: 

Electrolyte replenishers are substances used to restore or maintain the normal electrolyte balance in the body. Electrolytes are essential ions like Na⁺, K⁺, Ca²⁺, Cl⁻, HCO₃⁻, required for vital physiological functions. 

 

Common Electrolyte Replenishers: 

1. Sodium Chloride (NaCl): Maintains osmotic pressure and fluid balance. 

2. Potassium Chloride (KCl): Vital for muscle function and heart rhythm. 

3. Calcium Gluconate / Calcium Chloride: Used in hypocalcemia. 

4. Magnesium Sulfate: Used in eclampsia and magnesium deficiency. 

 

Uses: 

• Dehydration Treatment: Electrolyte solutions like ORS (oral rehydration salts) restore lost fluids and ions. 

• Electrolyte Imbalance: In cases of diarrhea, vomiting, kidney disorders. 

• IV Fluids: Electrolytes are part of intravenous fluids to maintain plasma electrolyte levels. 

• Cardiac Support: Potassium and calcium ions are critical in maintaining cardiac function. 

 

Formulations: 

• Oral Solutions: ORS, electrolyte powders. 

• Injectables: Ringer’s solution, saline, dextrose saline. 

 

Conclusion: 

Electrolyte replenishers are vital in medical emergencies and chronic conditions involving fluid or ion imbalance. Their proper administration ensures homeostasis, especially in pediatric, geriatric, and critically ill patients. 

48. Explain the principle and procedure of limit test for iron. 

Principle: 

The limit test for iron is a colorimetric test that detects and limits the amount of iron (Fe³⁺) present as an impurity in pharmaceutical substances. It is based on the formation of a pale pink to deep red color when iron reacts with thioglycolic acid in the presence of citric acid and an ammoniacal buffer. 

 

Reagents Used: 

1. Citric acid solution – acts as a complexing agent. 

2. Thioglycolic acid – reduces ferric (Fe³⁺) to ferrous (Fe²⁺) and forms a purple-red complex. 

3. Ammonia solution – adjusts pH. 

4. Iron standard solution – contains known concentration of iron. 

 

Procedure: 

1. Test Solution: 

1. Take the prescribed quantity of the substance under test. 

2. Dissolve in water, add 2 mL each of citric acid and thioglycolic acid. 

3. Add ammonia solution dropwise until pH becomes alkaline. 

4. Dilute with water to 50 mL and allow to stand for 5 minutes. 

2. Standard Solution: 

1. Prepare a solution with a known quantity of iron standard (typically 20 ppm). 

2. Treat it similarly as the test solution. 

3. Comparison: 

1. Compare the intensity of the purple-red color of the test and standard solutions against a white background. 

 

Observation: 

• If the test solution’s color is not more intense than the standard, the sample passes the test. 

• If it is darker, the sample fails the test. 

 

Conclusion: 

The limit test for iron ensures that iron impurities in pharmaceutical substances do not exceed pharmacopeial limits, as excess iron can catalyze oxidation and affect drug stability. 

49. Define impurities. Classify and explain their sources. 

Definition: 

Impurities are unwanted chemicals that remain with the active pharmaceutical ingredient (API) or develop during formulation or storage of pharmaceutical products. These may affect the efficacy, safety, and stability of the drug. 

 

Classification of Impurities: 

1. Organic Impurities: 

1. Starting materials 

2. By-products 

3. Degradation products 

4. Residual solvents 

2. Inorganic Impurities: 

1. Reagents 

2. Ligands 

3. Catalysts 

4. Heavy metals 

5. Inorganic salts 

3. Residual Solvents: 

1. Organic volatile chemicals used during synthesis. 

4. Physical Impurities: 

1. Dust, glass particles, filter fibers, etc. 

 

Sources of Impurities: 

1. Raw Materials: 

1. Impure or contaminated starting materials lead to impurities in the final product. 

2. Manufacturing Process: 

1. Incomplete reactions, side reactions, and contaminated processing equipment contribute impurities. 

3. Storage Conditions: 

1. Exposure to light, heat, air, or moisture can degrade products. 

4. Reagents and Solvents: 

1. Traces of solvents or reagents left behind after synthesis. 

5. Packaging Materials: 

1. Interaction of product with packaging can introduce leachables. 

6. Cross-contamination: 

1. Occurs during handling of multiple products using shared facilities. 

 

Conclusion: 

Identifying and controlling impurities is critical in pharmaceutical manufacturing. Regulatory bodies like ICH and pharmacopoeias set specific limits for permissible impurities to ensure the safety, purity, and therapeutic effectiveness of pharmaceutical substances. 

50. Write the preparation, assay and uses of potassium iodide. 

Preparation: 

Potassium iodide (KI) is prepared by reacting iodine (I₂) with potassium hydroxide (KOH): 

I₂ + 6KOH → 5KI + KIO₃ + 3H₂O 

The solution is then evaporated to crystallize KI. The resulting crystals are dried and purified. 

 

Assay (Pharmacopoeial Method – Iodometry): 

Principle: 

Potassium iodide is assayed by titration with potassium iodate (KIO₃) in acidic medium. The reaction liberates iodine, which is then titrated with sodium thiosulphate (Na₂S₂O₃) using starch as an indicator. 

Reaction: 

KIO₃ + 5KI + 6HCl → 3I₂ + 6KCl + 3H₂O 
I₂ + 2Na₂S₂O₃ → 2NaI + Na₂S₄O₆ 

Procedure: 

1. Dissolve a weighed quantity of KI in water. 

2. Add hydrochloric acid and potassium iodate to liberate iodine. 

3. Titrate the liberated iodine with sodium thiosulphate. 

4. Use starch solution as an indicator near the endpoint (blue to colorless). 

 

Uses: 

1. Iodine Source: Used as an iodine supplement in treatment and prevention of goitre and iodine deficiency. 

2. Expectorant: Promotes expulsion of mucus from respiratory tract. 

3. Radiation Protection: Protects the thyroid gland in nuclear radiation exposure by blocking radioactive iodine uptake. 

4. Iodine Solution Preparation: Used in preparation of Lugol’s Iodine (aqueous iodine solution). 

5. Syphilis Treatment (historical): Previously used in treatment of tertiary syphilis. 

 

Conclusion: 

Potassium iodide is a vital pharmaceutical agent due to its diverse medicinal applications and importance in thyroid-related therapies. 

51. What are cathartics? Give classification and uses. 

Definition: 

Cathartics are substances that promote evacuation of the bowels by accelerating defecation. They are used to relieve constipation, clear the bowel before diagnostic procedures, and remove ingested toxins. 

 

Classification of Cathartics: 

1. Bulk-forming Cathartics: 

1. Absorb water and increase stool bulk. 

2. Examples: Methylcellulose, Psyllium husk 

2. Stimulant Cathartics: 

1. Stimulate intestinal peristalsis directly. 

2. Examples: Senna, Bisacodyl, Castor oil 

3. Saline Cathartics (Osmotic): 

1. Draw water into the intestine via osmosis. 

2. Examples: Magnesium sulfate, Sodium phosphate 

4. Lubricant Cathartics: 

1. Soften stools and ease passage by lubrication. 

2. Example: Liquid paraffin 

5. Emollient (Stool Softeners): 

1. Increase water and fat content in stools. 

2. Example: Docusate sodium 

 

Uses of Cathartics: 

• Treatment of Constipation: Especially in chronic and acute cases. 

• Pre-operative Bowel Clearance: Before surgeries or diagnostic tests like colonoscopy. 

• Poisoning Management: Saline cathartics help in eliminating toxins. 

• Postpartum or Post-operative Use: To ease bowel movement in patients after surgery or childbirth. 

 

Important Note: 

Cathartics should be used cautiously in children, elderly, and patients with cardiovascular or renal disorders. Overuse can lead to electrolyte imbalance, dehydration, and dependency. 

 

Conclusion: 

Cathartics are essential drugs in gastrointestinal pharmacology. Their correct use, classification, and understanding help ensure effective and safe treatment of bowel irregularities. 

52. Explain the identification tests for anions. 

Identification tests for anions are qualitative analytical procedures used to confirm the presence of specific anions in inorganic substances. Each anion responds to a particular reagent or condition, producing a characteristic reaction (e.g., color change, precipitate). 

 

Common Anions and Their Identification Tests: 

1. Chloride (Cl⁻): 

1. Reagent: Silver nitrate (AgNO₃) 

2. Observation: Formation of a white precipitate of silver chloride (AgCl) that is soluble in ammonium hydroxide. 

3. Reaction: 
   Cl⁻ + AgNO₃ → AgCl↓ + NO₃⁻ 

2. Sulfate (SO₄²⁻): 

1. Reagent: Barium chloride (BaCl₂) in the presence of dilute HCl 

2. Observation: Formation of white precipitate of barium sulfate (BaSO₄) that is insoluble in HCl. 

3. Reaction: 
   SO₄²⁻ + BaCl₂ → BaSO₄↓ + 2Cl⁻ 

3. Carbonate (CO₃²⁻): 

1. Reagent: Dilute hydrochloric acid (HCl) 

2. Observation: Effervescence due to evolution of carbon dioxide (CO₂), which turns lime water milky. 

3. Reaction: 
   CO₃²⁻ + 2H⁺ → CO₂↑ + H₂O 

4. Phosphate (PO₄³⁻): 

1. Reagent: Ammonium molybdate in nitric acid 

2. Observation: Formation of a yellow precipitate of ammonium phosphomolybdate. 

3. Reaction: 
   PO₄³⁻ + 12MoO₄²⁻ + H⁺ → Yellow ppt. 

5. Nitrate (NO₃⁻): 

1. Reagent: Diphenylamine or ferrous sulfate (Brown ring test) 

2. Observation: Formation of a brown ring at the junction of the liquids. 

 

Conclusion: 

These tests help in confirming the presence of particular anions in pharmaceutical substances, ensuring their identity and quality per pharmacopeial standards. 

53. Describe pharmaceutical buffers with examples. 

Definition: 

Pharmaceutical buffers are solutions that resist change in pH when small amounts of acid or base are added. They are essential in maintaining the pH of formulations, ensuring drug stability, solubility, and biological compatibility. 

 

Components of Buffer: 

1. Weak acid + its salt with strong base 
   Example: Acetic acid + Sodium acetate 

2. Weak base + its salt with strong acid 
   Example: Ammonia + Ammonium chloride 

 

Types of Pharmaceutical Buffers: 

1. Acetate Buffer: 

1. Acetic acid + Sodium acetate 

2. pH range: 3.6–5.6 

3. Used in eye drops and ear drops. 

2. Phosphate Buffer: 

1. Sodium dihydrogen phosphate + Disodium hydrogen phosphate 

2. pH range: 6.0–8.0 

3. Common in parenteral preparations. 

3. Citrate Buffer: 

1. Citric acid + Sodium citrate 

2. pH range: 3.0–6.2 

3. Used in oral liquid formulations. 

 

Uses in Pharmacy: 

• Stabilization: Buffers maintain the pH within a required range, enhancing chemical stability of drugs. 

• Solubility: Some drugs are pH-sensitive; buffers help optimize solubility. 

• Patient Comfort: Adjusting pH to match body fluids (e.g., tears or plasma) avoids irritation. 

• Enzyme Activity: Enzyme-based formulations require specific pH for activity. 

• Compatibility: Ensures compatibility with biological systems and other formulation components. 

 

Examples: 

• Eye drops: pH 6.5–7.5 maintained using borate or phosphate buffers. 

• Injectable solutions: use phosphate or citrate buffers to mimic blood plasma pH. 

 

Conclusion: 

Pharmaceutical buffers are critical excipients that ensure product safety, efficacy, and comfort for the patient. Their selection depends on the required pH, stability, and route of administration. 

 

 

 

 

 

 

 

Pharmaceutical Inorganic Chemistry Long Question Answer [10 Marks] 

1. Define and classify acids, bases, and buffers. Explain the role of buffers in pharmacy. 

Acids: 

Acids are substances that donate protons (H⁺ ions) in aqueous solutions or accept electrons. They have a sour taste and turn blue litmus red. 

Examples: Hydrochloric acid (HCl), Acetic acid (CH₃COOH) 

Bases: 

Bases are substances that accept protons or donate hydroxide ions (OH⁻). They taste bitter and turn red litmus blue. 

Examples: Sodium hydroxide (NaOH), Ammonia (NH₃) 

 

Classifications: 

1. Based on Arrhenius Concept: 

• Acid: Produces H⁺ in water (e.g., HCl) 

• Base: Produces OH⁻ in water (e.g., NaOH) 

2. Based on Bronsted-Lowry Concept: 

• Acid: Proton donor 

• Base: Proton acceptor 

3. Based on Lewis Concept: 

• Acid: Electron pair acceptor 

• Base: Electron pair donor 

 

Buffers: 

A buffer is a solution that resists change in pH when small amounts of acid or base are added. It usually consists of a weak acid and its conjugate base or weak base and its conjugate acid. 

Examples: 

• Acetate buffer (CH₃COOH + CH₃COONa) 

• Phosphate buffer (NaH₂PO₄ + Na₂HPO₄) 

 

Role of Buffers in Pharmacy: 

1. Stability of Drugs: 

1. Many drugs are stable only at specific pH values. Buffers maintain this pH to prevent degradation. 

2. Biological Compatibility: 

1. Parenteral (injectable), ophthalmic (eye drops), and nasal preparations must have pH near physiological values to prevent irritation or tissue damage. 

3. Solubility and Absorption: 

1. Some drugs are pH-dependent for solubility and bioavailability. Buffers help maintain optimal pH for absorption. 

4. Enzyme Activity: 

1. Enzymes used in pharmaceutical preparations work best at specific pH ranges, maintained by buffers. 

5. Taste Masking: 

1. Adjusting pH can help reduce bitterness in oral solutions or syrups. 

6. Preservative Action: 

1. The efficacy of some preservatives (e.g., benzoic acid) depends on pH, hence buffers are used. 

 

Conclusion: 

Understanding acids, bases, and buffers is essential in pharmaceutical sciences. Buffers are vital excipients that not only ensure the drug remains stable and effective but also enhance patient comfort and compliance. They play a key role in product formulation, manufacturing, and administration routes like oral, topical, and parenteral. 

2. What is the limit test? Describe the principle and procedure of limit test for chloride and iron. 

(10 marks | 350–450 words) 

 

Definition of Limit Test: 

Limit test is a qualitative or semi-quantitative analytical procedure used to identify and control small quantities of impurities in pharmaceutical substances. It ensures that impurities do not exceed prescribed limits as specified in pharmacopeias (e.g., IP, BP, USP). 

Limit tests are simple, rapid, and sensitive methods to compare the level of impurity in a sample against a standard solution. 

 

Limit Test for Chloride (Cl⁻): 

Principle: 

The chloride ion in the sample reacts with silver nitrate in the presence of nitric acid to form silver chloride (AgCl), a white turbidity. The turbidity formed is compared with that produced by a standard chloride solution. 

Reaction: 
AgNO3+Cl−→AgCl↓+NO3−\text{AgNO}_3 + \text{Cl}^- \rightarrow \text{AgCl} \downarrow + \text{NO}_3^-AgNO3 +Cl−→AgCl↓+NO3−  

 

Procedure: 

1. Take 1 g of the substance to be tested and dissolve it in distilled water. 

2. Add 1 mL of dilute nitric acid to acidify the solution. 

3. Add 1 mL of 0.1 N silver nitrate solution. 

4. Make up the volume to 50 mL with distilled water. 

5. Prepare a standard solution containing a known amount of chloride (e.g., 0.05845 g NaCl in 1000 mL water = 1 mL ≈ 1 µg Cl⁻). 

6. Compare the turbidity of both solutions after 5 minutes. 

 

Limit Test for Iron (Fe³⁺): 

Principle: 

Iron present in the sample reacts with thioglycolic acid in an ammoniacal medium to form a pink to reddish-purple color (ferrous thioglycolate complex). The intensity of color is compared with a standard iron solution. 

Reaction: 
Fe3++HSCH2COOH+NH3→Ferrous thioglycolate (colored complex)\text{Fe}^{3+} + \text{HSCH}_2\text{COOH} + \text{NH}_3 \rightarrow \text{Ferrous thioglycolate (colored complex)}Fe3++HSCH2 COOH+NH3 →Ferrous thioglycolate (colored complex) 

 

Procedure: 

1. Dissolve the sample in distilled water in a Nessler’s cylinder. 

2. Add 2 mL of thioglycolic acid and ammonia solution to make it slightly alkaline (pH ~8.5). 

3. Dilute to 50 mL with water and allow to stand for 5 minutes. 

4. Prepare a standard iron solution (typically contains 20 ppm Fe³⁺). 

5. Compare the color intensity of test and standard under daylight. 

 

Significance: 

• Ensures product purity and safety. 

• Confirms compliance with IP standards. 

• Prevents toxicity or side effects caused by excess impurities. 

 

Conclusion: 

Limit tests for chloride and iron are vital to monitor and control impurities in pharmaceutical substances. They ensure the quality of raw materials and finished products, thus playing a critical role in drug safety and regulatory compliance. 

3. Define and classify antacids. Write in detail about official compounds used as antacids. 

(10 marks | 350–450 words) 

 

Definition of Antacids: 

Antacids are basic substances that neutralize excess gastric acid (HCl) in the stomach and provide relief from acidity, heartburn, and indigestion. They are commonly used in the treatment of hyperacidity, gastritis, and peptic ulcers. 

 

Classification of Antacids: 

Antacids are classified into the following types: 

A. Based on Absorption: 

1. Systemic Antacids: 

1. Absorbed into systemic circulation. 

2. Rapid action but may cause alkalosis. 

3. Example: Sodium bicarbonate 

2. Non-Systemic Antacids: 

1. Not absorbed; act locally in the stomach. 

2. Fewer systemic side effects. 

3. Examples: Magnesium hydroxide, Aluminium hydroxide 

 

B. Based on Chemical Composition: 

1. Inorganic Antacids: 

1. Sodium bicarbonate, Magnesium hydroxide, Aluminium hydroxide, Calcium carbonate 

2. Organic Antacids: 

1. Alginates, Simethicone (usually used in combination) 

 

Official Compounds Used as Antacids (as per IP): 

1. Sodium Bicarbonate (NaHCO₃): 

• Type: Systemic antacid 

• Action: Neutralizes HCl to form NaCl, CO₂, and water. 
  NaHCO3+HCl→NaCl+CO2+H2O\text{NaHCO}_3 + \text{HCl} \rightarrow \text{NaCl} + \text{CO}_2 + \text{H}_2\text{O}NaHCO3 +HCl→NaCl+CO2 +H2 O 

• Limitations: Causes gastric distension due to CO₂ release; may lead to systemic alkalosis on prolonged use. 

 

2. Magnesium Hydroxide (Mg(OH)₂): 

• Type: Non-systemic, fast-acting 

• Action: Neutralizes acid to form MgCl₂ and water. 
  Mg(OH)2+2HCl→MgCl2+2H2O\text{Mg(OH)}_2 + 2\text{HCl} \rightarrow \text{MgCl}_2 + 2\text{H}_2\text{O}Mg(OH)2 +2HCl→MgCl2 +2H2 O 

• Additional Benefit: Mild laxative effect, useful when combined with Aluminium hydroxide. 

 

3. Aluminium Hydroxide (Al(OH)₃): 

• Type: Non-systemic, slow-acting 

• Action: Forms AlCl₃ and water with HCl. 
  Al(OH)3+3HCl→AlCl3+3H2O\text{Al(OH)}_3 + 3\text{HCl} \rightarrow \text{AlCl}_3 + 3\text{H}_2\text{O}Al(OH)3 +3HCl→AlCl3 +3H2 O 

• Additional Property: Causes constipation. 

Note: Often used in combination with magnesium salts to balance GI side effects. 

 

4. Calcium Carbonate (CaCO₃): 

• Action: Neutralizes HCl to form CaCl₂, CO₂, and water. 
  CaCO3+2HCl→CaCl2+CO2+H2O\text{CaCO}_3 + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{CO}_2 + \text{H}_2\text{O}CaCO3 +2HCl→CaCl2 +CO2 +H2 O 

• Drawback: Rebound hyperacidity; risk of kidney stones with prolonged use. 

 

Ideal Properties of Antacids: 

• Fast-acting and long-lasting 

• Non-toxic and palatable 

• Do not interfere with digestion 

• Do not cause systemic alkalosis 

 

Conclusion: 

Antacids are an essential class of pharmaceutical agents used to manage acid-related disorders. The choice between systemic and non-systemic agents depends on efficacy, side effects, and patient condition. Official compounds like magnesium hydroxide and aluminium hydroxide are commonly preferred due to their safety and effectiveness. 

4. Define and classify impurities. Write in detail about various sources of impurities in pharmaceutical substances. 

(10 marks | 350–450 words) 

 

Definition of Impurities: 

Impurities are unwanted chemicals that remain with the active pharmaceutical ingredient (API) or develop during formulation or aging of both API and formulated products. These impurities may affect the safety, efficacy, and quality of pharmaceutical products. 

 

Classification of Impurities: 

1. Organic Impurities: 

1. Arise from the manufacturing process, starting materials, intermediates, or degradation. 

2. Examples: Starting materials, by-products, intermediates. 

2. Inorganic Impurities: 

1. Include reagents, ligands, catalysts, heavy metals, salts, or other materials used in the manufacturing process. 

2. Examples: Sulphate, chloride, iron, heavy metals. 

3. Residual Solvents: 

1. Organic volatile chemicals used or produced in the manufacture. 

2. Classified into: 

1. Class I: Avoidable (e.g., benzene, carbon tetrachloride) 

2. Class II: Limited use (e.g., methanol, acetonitrile) 

3. Class III: Low toxic potential (e.g., ethanol, acetone) 

4. Foreign Matter: 

1. Physical contaminants such as glass, dust, hair, metal pieces. 

 

Sources of Impurities: 

1. Raw Materials: 

• Impurities may originate from natural sources (minerals or biologicals) or from poor-quality chemicals. 

• Example: Sand, clay in natural substances. 

2. Manufacturing Process: 

• Chemical reactions may be incomplete or produce by-products. 

• Example: Reagent excess, catalyst residue. 

3. Storage Conditions: 

• Moisture, temperature, and light can degrade products and form impurities. 

• Example: Oxidation of ferrous sulfate to ferric form. 

4. Equipment Contamination: 

• Improperly cleaned equipment can introduce oil, grease, or metal particles. 

5. Packaging Materials: 

• Leaching of chemicals from plastic or rubber containers. 

• Example: Phthalates from plastic containers. 

6. Cross-Contamination: 

• From adjacent production lines or during handling and transfer. 

7. Environmental Contamination: 

• Dust, air pollutants, or water impurities entering during processing. 

 

Importance of Controlling Impurities: 

• To ensure patient safety 

• To comply with regulatory standards (IP, BP, USP) 

• To maintain product quality, efficacy, and shelf-life 

 

Conclusion: 

Impurities, though often present in small amounts, can significantly affect the quality and therapeutic efficacy of pharmaceutical products. Identifying, quantifying, and controlling these impurities through limit tests and validation procedures is essential for compliance and patient safety. 

5. Define and classify electrolytes. Explain the physiological role of major electrolytes in the body. 

(10 marks | 350–450 words) 

 

Definition of Electrolytes: 

Electrolytes are substances that dissociate into ions when dissolved in water and conduct electricity. They are essential for various physiological functions, including nerve conduction, muscle contraction, hydration, and acid-base balance. 

 

Classification of Electrolytes: 

Electrolytes are mainly classified into: 

1. Based on the charge: 

• Cations (positively charged ions): 

• Sodium (Na⁺) 

• Potassium (K⁺) 

• Calcium (Ca²⁺) 

• Magnesium (Mg²⁺) 

• Anions (negatively charged ions): 

• Chloride (Cl⁻) 

• Bicarbonate (HCO₃⁻) 

• Phosphate (PO₄³⁻) 

• Sulphate (SO₄²⁻) 

2. Based on location: 

• Intracellular Electrolytes: 

• Predominantly Potassium (K⁺), Magnesium (Mg²⁺), and Phosphate (PO₄³⁻) 

• Extracellular Electrolytes: 

• Mainly Sodium (Na⁺), Chloride (Cl⁻), and Bicarbonate (HCO₃⁻) 

 

Physiological Role of Major Electrolytes: 

1. Sodium (Na⁺): 

• Main extracellular cation. 

• Regulates osmotic pressure, fluid balance, and nerve impulse transmission. 

• Deficiency: Hyponatremia (leads to confusion, fatigue) 

• Excess: Hypernatremia (causes dehydration and hypertension) 

2. Potassium (K⁺): 

• Main intracellular cation. 

• Essential for nerve function, muscle contraction, especially in the heart. 

• Deficiency: Hypokalemia (leads to arrhythmia) 

• Excess: Hyperkalemia (can cause cardiac arrest) 

3. Calcium (Ca²⁺): 

• Involved in bone formation, blood coagulation, enzyme activation, and muscle contraction. 

• Maintains membrane integrity and neuromuscular function. 

• Deficiency: Hypocalcemia (tetany, muscle spasms) 

4. Magnesium (Mg²⁺): 

• Co-factor for over 300 enzymatic reactions. 

• Important in neuromuscular function and cardiac health. 

• Deficiency: Weakness, cramps, cardiac abnormalities 

5. Chloride (Cl⁻): 

• Main extracellular anion. 

• Helps maintain acid-base balance and osmotic pressure. 

• Combines with hydrogen to form HCl in the stomach. 

6. Bicarbonate (HCO₃⁻): 

• Acts as a buffer to maintain pH balance in blood. 

• Regulates acid-base homeostasis along with kidneys and lungs. 

7. Phosphate (PO₄³⁻): 

• Component of ATP, DNA, and RNA. 

• Involved in bone mineralization and energy metabolism. 

 

Conclusion: 

Electrolytes play a crucial role in maintaining physiological stability, and imbalances can lead to serious health complications. Pharmaceutical preparations often include electrolyte replenishing agents to restore normal body function, especially in cases of dehydration, diarrhea, or electrolyte loss due to illness. 

6. Define and classify acids and bases. Discuss in detail about pharmaceutical buffers. 

(10 marks | 350–450 words) 

 

Definition: 

• Acids are substances that release hydrogen ions (H⁺) in aqueous solutions. 

• Bases are substances that release hydroxide ions (OH⁻) or accept hydrogen ions. 

 

Classification of Acids and Bases: 

1. Based on Strength: 

• Strong Acids: Completely ionize in water 
  Examples: HCl, H₂SO₄ 

• Weak Acids: Partially ionize 
  Examples: Acetic acid, Carbonic acid 

• Strong Bases: Fully dissociate in water 
  Examples: NaOH, KOH 

• Weak Bases: Partially dissociate 
  Examples: Ammonia (NH₃), Magnesium hydroxide 

2. According to Arrhenius Theory: 

• Acid: Produces H⁺ ions in water 

• Base: Produces OH⁻ ions in water 

3. According to Bronsted-Lowry Theory: 

• Acid: Proton donor 

• Base: Proton acceptor 

4. According to Lewis Theory: 

• Acid: Electron pair acceptor 

• Base: Electron pair donor 

 

Pharmaceutical Buffers: 

Definition: 

A buffer is a solution that resists changes in pH when small amounts of acid or base are added. It consists of a weak acid and its conjugate base or a weak base and its conjugate acid. 

Common Examples: 

• Acidic Buffer: Acetic acid + Sodium acetate 

• Basic Buffer: Ammonia + Ammonium chloride 

• Pharmaceutical Buffer: Phosphate buffer (NaH₂PO₄ + Na₂HPO₄) 

 

Role and Importance in Pharmacy: 

1. Stability of Drugs: 

1. Many drugs are pH-sensitive. 

2. Buffers help maintain a stable environment, ensuring drug efficacy and shelf-life. 

2. Compatibility with Body Fluids: 

1. Blood and tissue fluids have a narrow pH range (7.35–7.45). 

2. Buffered preparations reduce irritation and ensure patient comfort. 

3. Enhancing Solubility and Absorption: 

1. Some drugs are better absorbed at specific pH levels. 

2. Buffers maintain optimal pH for maximum bioavailability. 

4. In Ophthalmic and Parenteral Preparations: 

1. Buffers ensure isotonicity and maintain physiological pH, thus preventing damage to sensitive tissues. 

5. Microbial Control: 

1. Some buffers maintain pH to prevent bacterial growth. 

 

Applications of Pharmaceutical Buffers: 

• Eye drops (e.g., borate buffer in ophthalmics) 

• Injectable solutions 

• Oral suspensions and syrups 

• Diagnostic reagents and biochemical assays 

 

Conclusion: 

Understanding acids, bases, and buffers is essential in pharmacy for formulating stable, safe, and effective pharmaceutical preparations. Buffers play a vital role in maintaining the pH balance, thereby enhancing the therapeutic performance of drugs. 

7. Define and classify cathartics. Discuss the official compounds used as cathartics. 

(10 marks | 350–450 words) 

 

Definition of Cathartics: 

Cathartics are drugs or agents that promote defecation by accelerating bowel movement and easing the passage of stool. They are used to relieve constipation, clear the bowel before diagnostic procedures, or eliminate toxic substances. 

 

Classification of Cathartics: 

Cathartics are broadly classified based on their mechanism of action: 

1. Stimulant Cathartics: 

• Act by stimulating intestinal mucosa and increasing peristalsis. 

• Examples: 

• Senna 

• Bisacodyl 

• Castor oil 

2. Bulk-forming Cathartics: 

• Increase bulk and water content of the stool. 

• Mimic natural dietary fiber. 

• Examples: 

• Psyllium husk 

• Methylcellulose 

3. Saline (Osmotic) Cathartics: 

• Draw water into the intestinal lumen by osmosis, softening stool and promoting evacuation. 

• Examples: 

• Magnesium sulphate (Epsom salt) 

• Sodium sulphate 

• Sodium phosphate 

4. Lubricant Cathartics: 

• Lubricate the intestinal walls, facilitating passage of feces. 

• Examples: 

• Liquid paraffin 

• Mineral oil 

5. Fecal Softeners (Emollient Laxatives): 

• Allow water and fat to mix with feces, softening stool. 

• Example: 

• Docusate sodium 

 

Official Compounds Used as Cathartics (IP/BP/USP): 

1. Magnesium Sulphate (MgSO₄·7H₂O): 

• Official in IP. 

• Saline cathartic; acts by retaining water in the intestine. 

• Used for rapid bowel evacuation and treating poisoning. 

• Dose: 5–15 g orally in water. 

2. Sodium Potassium Tartrate (Rochelle Salt): 

• A mild saline cathartic. 

• Acts by osmotic action. 

• Often used in combination with sodium bicarbonate in effervescent laxatives. 

3. Castor Oil: 

• Natural vegetable oil. 

• On hydrolysis, releases ricinoleic acid which irritates the intestinal mucosa and induces peristalsis. 

• Used in acute constipation and pre-operative bowel clearance. 

4. Senna Extract (Standardized): 

• Herbal stimulant cathartic containing sennosides. 

• Stimulates colonic motility. 

• Official in IP. 

 

Pharmaceutical Uses of Cathartics: 

• Relief from constipation 

• Bowel preparation before surgery or colonoscopy 

• Removal of toxins in poisoning 

• Adjunct therapy in anthelmintic treatments 

 

Conclusion: 

Cathartics are an essential class of drugs in pharmaceutical practice. Understanding their types, mechanisms, and official compounds helps pharmacists recommend appropriate agents for different clinical needs, ensuring safe and effective bowel management. 

8. Explain the principle, procedure and significance of limit test for heavy metals and chloride. 

(10 marks | 350–450 words) 

 

A. Limit Test for Heavy Metals 

Principle: 

The limit test for heavy metals is based on the formation of colored sulfide precipitates of heavy metals (like lead, mercury, etc.) when treated with hydrogen sulfide (H₂S) in an acidic medium. The intensity of color produced in the test solution is compared with that of a standard solution containing a known quantity of heavy metals, usually expressed as lead (Pb). 

Reagent Used: 

• Hydrogen sulfide water or thioacetamide reagent 

• Acetic acid 

• Standard lead solution 

Procedure: 

1. Dissolve the specified amount of the substance in water or prescribed solvent. 

2. Add acetic acid to acidify the solution. 

3. Add hydrogen sulfide reagent or thioacetamide and allow to stand for 5 minutes. 

4. Prepare a standard lead solution similarly. 

5. Compare both solutions against a white background. 

Observation: 

• If the color in the test solution is not darker than the standard, the sample passes the test. 

Significance: 

• Ensures the toxic heavy metal content is below permissible limits. 

• Protects patients from toxic effects like nephrotoxicity and neurotoxicity. 

 

B. Limit Test for Chloride 

Principle: 

This test is based on the precipitation of chloride ions as silver chloride (AgCl) when treated with silver nitrate (AgNO₃) in the presence of nitric acid (HNO₃). The turbidity produced is compared with a standard containing a known amount of chloride (usually as NaCl). 

Reagents Used: 

• Nitric acid 

• Silver nitrate solution 

• Standard sodium chloride solution 

Procedure: 

1. Dissolve the given quantity of the test substance in water. 

2. Add dilute nitric acid to acidify. 

3. Add 1 ml of silver nitrate solution. 

4. Shake and allow to stand for 5 minutes. 

5. Prepare a standard chloride solution similarly. 

6. Compare the opalescence or turbidity of both solutions. 

Observation: 

• If the test solution is not more turbid than the standard, the sample passes the test. 

Significance: 

• Ensures that excess chloride ions, which may affect the stability or safety of pharmaceutical substances, are within acceptable limits. 

 

Conclusion: 

Limit tests for heavy metals and chlorides are crucial quality control tools in pharmaceutical industries. They help in detecting and restricting impurities to ensure safety, efficacy, and compliance with pharmacopeial standards. 

9. What are antacids? Classify and explain the role and importance of antacids in pharmaceutical preparations. 

(10 marks | 350–450 words) 

 

Definition of Antacids: 

Antacids are pharmaceutical substances that neutralize excess gastric acid in the stomach and provide relief from hyperacidity, heartburn, and indigestion. They work by raising the pH of gastric contents, thereby reducing irritation of the stomach lining. 

 

Classification of Antacids: 

A. Based on Systemic or Non-systemic Action: 

1. Systemic Antacids: 

1. Absorbed into the bloodstream. 

2. Provide quick but short-term relief. 

3. Example: Sodium bicarbonate (NaHCO₃) 

2. Non-systemic Antacids: 

1. Not absorbed; act locally in the stomach. 

2. Provide longer-lasting effect. 

3. Examples: 

1. Magnesium hydroxide (Mg(OH)₂) 

2. Aluminium hydroxide gel (Al(OH)₃) 

3. Calcium carbonate (CaCO₃) 

 

B. Based on Chemical Composition: 

1. Alkaline salts of sodium: 

1. Sodium bicarbonate 

2. Magnesium compounds: 

1. Magnesium oxide, magnesium hydroxide, magnesium trisilicate 

3. Aluminium compounds: 

1. Aluminium hydroxide gel, aluminium phosphate 

4. Calcium compounds: 

1. Calcium carbonate 

5. Combinations: 

1. Magaldrate (aluminium + magnesium) 

2. Gelusil (magnesium hydroxide + aluminium hydroxide + simethicone) 

 

Role and Importance of Antacids: 

1. Neutralization of Gastric Acid: 

• Antacids neutralize hydrochloric acid (HCl) in the stomach, alleviating conditions like: 

• Gastritis 

• Peptic ulcer 

• Gastroesophageal reflux disease (GERD) 

2. Protection of Gastric Mucosa: 

• Some antacids form a protective layer over the stomach lining, preventing further damage. 

3. Immediate Relief: 

• Especially systemic antacids (e.g., sodium bicarbonate) provide quick relief in acute cases. 

4. Used in Combination Therapies: 

• Antacids are often combined with anti-flatulent agents like simethicone to reduce bloating and gas. 

• Also used alongside H₂ blockers or proton pump inhibitors in long-term acid control. 

5. Use in Acidic Drug Overdose: 

• In poisoning with acidic drugs, antacids may be used to neutralize systemic acidosis (systemic antacids like sodium bicarbonate). 

 

Limitations and Side Effects: 

• Sodium bicarbonate: Can cause alkalosis, sodium overload, and rebound acidity. 

• Calcium salts: Risk of kidney stones or hypercalcemia. 

• Magnesium salts: May cause diarrhea. 

• Aluminium salts: Can cause constipation and phosphate depletion. 

 

Conclusion: 

Antacids play a significant role in managing gastrointestinal conditions related to acid imbalance. Their proper selection based on patient profile (e.g., avoiding sodium salts in hypertension) is essential for safety and efficacy in pharmaceutical practice. 

10. Write in detail the principle and procedure of the limit test for chloride, sulphate, and iron. 

(10 marks | 350–450 words) 

 

1. Limit Test for Chloride 

Principle: 

This test is based on the precipitation of chloride ions as silver chloride (AgCl) when treated with silver nitrate in an acidic medium. The turbidity produced is compared with a standard chloride solution. 

Reagents Used: 

• Dilute nitric acid 

• Silver nitrate solution 

• Standard sodium chloride solution 

Procedure: 

1. Dissolve the specified amount of the test substance in water. 

2. Add 1 ml of dilute nitric acid. 

3. Make up the volume to 50 ml with water. 

4. Add 1 ml of silver nitrate solution. 

5. Shake well and allow to stand for 5 minutes. 

6. Prepare a standard chloride solution using 1 ml of standard NaCl. 

7. Compare the turbidity of both solutions against a dark background. 

Observation: 

The turbidity of the test solution should not be more than that of the standard. 

 

2. Limit Test for Sulphate 

Principle: 

This test is based on the precipitation of sulphate ions (SO₄²⁻) as barium sulphate (BaSO₄) in the presence of barium chloride and hydrochloric acid. The turbidity is measured against a standard solution. 

Reagents Used: 

• Dilute hydrochloric acid 

• Barium chloride reagent 

• Ethanol (for dispersing precipitate) 

• Standard potassium sulphate solution 

Procedure: 

1. Dissolve the test substance in 45 ml water. 

2. Add 2 ml of dilute HCl and 3 ml of barium chloride solution. 

3. Stir well and keep for 5 minutes. 

4. Prepare a standard sulphate solution with known amount of K₂SO₄. 

5. Compare the turbidity of test and standard against a black background. 

Observation: 

The turbidity of the test solution should not exceed that of the standard. 

 

3. Limit Test for Iron 

Principle: 

This test is based on the reaction of iron ions (Fe³⁺) with thioglycolic acid or ammonium thiocyanate in the presence of a buffer to form a purple or reddish complex. The intensity is compared with a standard iron solution. 

Reagents Used: 

• Citric acid 

• Thioglycolic acid or ammonium thiocyanate 

• Ammonia/ammonium chloride buffer 

• Standard iron solution 

Procedure: 

1. Dissolve the sample in 40 ml water. 

2. Add 2 ml of citric acid and thioglycolic acid. 

3. Add ammonia buffer to adjust pH and make volume to 50 ml. 

4. Prepare a standard iron solution with 20 µg of Fe. 

5. After 5 minutes, compare the purple color intensity. 

Observation: 

The color of the test solution should not be more intense than the standard. 

 

Conclusion: 

Limit tests are crucial in detecting and ensuring that impurities like chloride, sulphate, and iron remain within pharmacopeial limits. They help maintain drug purity and safety for therapeutic use. 

11. Define and classify dental products. Describe any two official dental products with preparation and uses. 

(10 marks | 350–450 words) 

 

Definition of Dental Products: 

Dental products are pharmaceutical preparations that are specifically used to clean, protect, or treat the teeth, gums, and oral cavity. These products help in maintaining oral hygiene, preventing tooth decay, gum diseases, and treating various oral infections. 

 

Classification of Dental Products: 

1. Dentifrices (Tooth Cleaners): 

1. Toothpastes 

2. Tooth powders 

3. Tooth gels 

2. Anti-caries Agents: 

1. Sodium fluoride 

2. Stannous fluoride 

3. Desensitizing Agents: 

1. Potassium nitrate 

2. Strontium chloride 

4. Astringents and Anti-plaque Agents: 

1. Chlorhexidine 

2. Zinc salts 

5. Antiseptics and Mouthwashes: 

1. Hydrogen peroxide 

2. Povidone iodine 

3. Listerine 

6. Oral Analgesics: 

1. Benzocaine 

2. Lidocaine gels 

7. Whitening Agents: 

1. Hydrogen peroxide 

2. Carbamide peroxide 

 

Official Dental Products: 

1. Sodium Fluoride (NaF): 

Category: Anti-caries agent (official in IP) 

Preparation: 

• Prepared by neutralizing hydrofluoric acid with sodium carbonate or sodium hydroxide: 

HF+NaOH→NaF+H2OHF + NaOH \rightarrow NaF + H₂OHF+NaOH→NaF+H2 O  

Properties: 

• White, crystalline powder 

• Soluble in water 

• Stable and odorless 

Uses: 

• Added to toothpastes and mouth rinses to prevent dental caries. 

• Strengthens enamel by forming fluorapatite, which is more resistant to acid attacks. 

• Also used in fluoridation of drinking water in small concentrations. 

 

2. Hydrogen Peroxide (H₂O₂): 

Category: Antiseptic and bleaching agent (official in IP as 6% w/v solution) 

Preparation: 

• Industrially prepared by anthraquinone process or electrolytic method. 

Properties: 

• Colorless liquid with a slightly sharp odor. 

• Decomposes on exposure to light and heat. 

• Stored in dark amber bottles with stabilizers. 

Uses in Dentistry: 

• Used as a mouthwash in diluted form (1.5%–3%) for oral ulcers, sore gums, and oral hygiene. 

• Acts by releasing nascent oxygen, which has bactericidal action. 

• Also used for teeth whitening (bleaching) in higher concentrations. 

 

Conclusion: 

Dental products are essential in maintaining oral and dental health. Compounds like sodium fluoride and hydrogen peroxide are officially recognized agents with established uses in preventing caries, treating infections, and ensuring overall dental care. 

12. What are acidifying and alkalinising agents? Explain with suitable examples and their pharmaceutical applications. 

(10 marks | 350–450 words) 

 

Definition: 

Acidifying agents are substances used to lower the pH of a pharmaceutical formulation, while alkalinising agents are used to raise the pH. They help in adjusting the pH to ensure stability, solubility, and therapeutic efficacy of the formulation. 

 

1. Acidifying Agents 

Definition: 

Acidifying agents are used to make solutions more acidic or to maintain an acidic environment in pharmaceutical preparations. 

Examples: 

• Dilute hydrochloric acid 

• Citric acid 

• Acetic acid 

• Phosphoric acid 

• Ascorbic acid 

• Ammonium chloride (systemic acidifier) 

Pharmaceutical Applications: 

• Citric acid is used in effervescent formulations and syrups to improve taste and act as a preservative. 

• Hydrochloric acid is used in the preparation of acidic solutions for injections. 

• Ascorbic acid acts as both an acidifier and antioxidant. 

• Ammonium chloride is used in systemic acidification (e.g., to treat alkalosis or promote excretion of basic drugs). 

 

2. Alkalinising Agents 

Definition: 

Alkalinising agents are used to increase the pH of solutions or to maintain an alkaline environment. 

Examples: 

• Sodium bicarbonate 

• Sodium citrate 

• Sodium acetate 

• Potassium citrate 

• Sodium carbonate 

Pharmaceutical Applications: 

• Sodium bicarbonate is commonly used as an antacid and also in oral rehydration salts (ORS). 

• Sodium citrate acts as a buffer and anticoagulant in blood preservation. 

• Potassium citrate is used in the treatment of urinary tract infections and to prevent kidney stones. 

• Sodium carbonate is used to alkalinize urine and in some tablet formulations. 

 

Role in Pharmacy: 

• pH adjustment: Many drugs are only stable or soluble at certain pH levels. 

• Bioavailability: Drugs must be in ionized or unionized form depending on the site of action; acidifiers or alkalinizers help achieve that. 

• Preservation: pH control prevents microbial growth. 

• Patient Comfort: Some drugs irritate the stomach unless buffered properly. 

 

Conclusion: 

Acidifying and alkalinising agents play a vital role in pharmaceutical formulation and therapy. They help optimize drug action, maintain product stability, and ensure compatibility, making them essential excipients in pharmacy. 

 

 

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