20. MISCELLANEOUS COMPOUNDS

Miscellaneous Compounds – Overview

In pharmacy, several inorganic compounds are grouped under miscellaneous compounds because of their varied uses. The most important categories include:

  1. Sclerosing Agents
  2. Expectorants
  3. Sedatives

1. Sclerosing Agents

Sclerosing agents are substances used to intentionally damage or close abnormal veins or tissues — commonly in the treatment of varicose veins or hemorrhoids. The important inorganic sclerosing agents are:

a) Sodium Tetradecyl Sulphate

Molecular Formula: C14H29NaO4S

  • Properties: White, odorless, waxy solid; soluble in water, alcohol, and ether.
  • Preparation: Formed by reacting tetradecyl alcohol with chlorosulfonic acid to form hydrogen sulphate ester, which is then neutralized with sodium carbonate to yield sodium tetradecyl sulphate.
  • Uses: Used as a buffered solution for the obliteration of varicose veins and internal hemorrhoids; also used as a wetting agent for spreading antiseptics.

b) Hypertonic Saline (Sodium Chloride Solution)

Synonym: Sodium chloride hypertonic saline (1.52–1.68% NaCl)

Composition: Sodium chloride – 16 g; Water for injection – up to 1000 ml.

  • Properties: Clear, colorless solution with slightly alkaline taste.
  • Preparation: Dissolve 16 g of NaCl in water for injection, adjust to 1000 ml, and sterilize.
  • Assay: Performed by Volhard’s back titration method using silver nitrate and ferric ammonium sulphate indicator.
  • Uses: Used as a sclerosing agent and also during surgical procedures for vein treatment.

2. Expectorants

Expectorants are drugs that promote the expulsion of mucus from the respiratory tract. Common inorganic expectorants include Potassium Citrate and Potassium Iodide.

a) Potassium Citrate

Synonyms: Kalii Citras, Tripotassium Citrate

Molecular Formula: C6H5O7K3·H2O

  • Properties: Odorless, white crystalline powder with a cooling saline taste; soluble in water and glycerol, insoluble in alcohol.
  • Limits: Should contain between 99–101% of potassium citrate.
  • Preparation: Made by neutralizing citric acid with potassium bicarbonate or potassium carbonate:
    3 KHCO3 + H3C6H5O7 → C6H5O7K3 + 3 CO2 + 3 H2O
  • Assay: Determined by back titration using sulphuric acid and NaOH with methyl orange indicator.
  • Storage: Store in a tightly closed container.
  • Uses: Acts as an osmotic diuretic, expectorant, mild laxative, and systemic alkalizing agent.

b) Potassium Iodide

Molecular Formula: KI

  • Properties: Colorless, opaque crystals with a slight odor; soluble in water, alcohol, and glycerol.
  • Preparation: Iodine reacts with iron filings to form ferroferric iodide, which decomposes in the presence of potassium carbonate to form potassium iodide:
    Fe + I2 → FeI2
    FeI2 + 2 FeI3 + K2CO3 → 8 KI + FeO·Fe2O3 + CO2
  • Assay: Iodometric titration using potassium iodate as titrant in acidic medium with chloroform.
  • Storage: Store in a well-closed container away from light and moisture.
  • Uses: Used in thyroid deficiency, as an expectorant in cough, and as a mild antifungal and reducing agent.

3. Sedatives

Sedatives are agents that calm the nervous system and are used to treat restlessness, anxiety, and mild mental disturbances. The most important inorganic sedative is Potassium Bromide.

Potassium Bromide

Molecular Formula: KBr

  • Properties: Colorless or white crystalline powder; odorless with a saline taste; soluble in water and glycerol, sparingly soluble in alcohol.
  • Preparation: Bromine reacts with potassium hydroxide to produce potassium bromide and bromate. The bromate is then reduced using charcoal:
    6 KOH + 3 Br2 → KBrO3 + 5 KBr + 3 H2O
    KBrO3 + 3 C → KBr + 3 CO
  • Assay: Performed by Volhard’s back titration using silver nitrate and ferric alum as an indicator.
  • Uses: Used as a sedative for treating anxiety and mental excitement. It is also used as an anticonvulsant in some neurological disorders.

Detailed Notes:

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