Question

Tincture of iodine has antiseptic properties. This solution is made by dissolving :

• A. iodine in potassium iodide
• B. iodine in acetone
• C. iodine in alcohol
• D. iodine in water

Hint:

The word "tincture" usually implies that {alcohol} is the solvent. So, Tincture of Iodine = Iodine dissolved in Alcohol (often with water and an iodide salt like KI to help dissolve more iodine). The key part to remember for "tincture" is the alcohol.

Answer 1

The Correct Option is C

Concept: Tincture of iodine is a common antiseptic, and its composition involves specific solutes and a solvent. Step 1: Understanding "Tincture" In a pharmaceutical context, a "tincture" generally refers to a solution where alcohol (ethanol) or a mixture of alcohol and water is used as the solvent. Step 2: Composition of Tincture of Iodine Tincture of iodine is an antiseptic solution primarily composed of:
Solute: Iodine (\(I_2\))
Solvent: A mixture of ethanol (alcohol) and water. Sometimes, potassium iodide (\(KI\)) or sodium iodide (\(NaI\)) is also added to increase the solubility of iodine in the aqueous-alcoholic solution (iodine itself is not very soluble in plain water but dissolves better in iodide solutions due to the formation of triiodide ions, \(I_3^-\)). However, the primary solvent characterising it as a "tincture" is alcohol. The question asks what iodine is dissolved in to make the solution. Step 3: Analyzing the options
(1) iodine in potassium iodide: While potassium iodide is often used to help dissolve iodine, potassium iodide itself is usually dissolved in water or an alcohol-water mixture. This option is incomplete as it doesn't specify the main solvent.
(2) iodine in acetone: Acetone can dissolve iodine, but solutions in acetone are not typically referred to as "tincture of iodine."
(3) iodine in alcohol: This aligns with the definition of a tincture. Tincture of iodine is iodine dissolved in alcohol (usually ethanol), often with some water and potentially an iodide salt.
(4) iodine in water: Iodine has low solubility in pure water. Solutions of iodine in water (like Lugol's iodine) usually require potassium iodide to achieve a useful concentration. Step 4: Identifying the best description Given the term "tincture," the primary solvent system involves alcohol. Therefore, dissolving "iodine in alcohol" is the most direct and defining characteristic. Standard tincture of iodine typically contains 2-7% elemental iodine, along with potassium iodide or sodium iodide, dissolved in a mixture of ethanol and water. The alcohol is a key component.