Write down the purity test of sugar of milk.

🧪 Purity Test of Sugar of Milk (Lactose)

In homeopathy and pharmaceutical contexts, sugar of milk (lactose) must meet high purity standards. Here’s how its purity is typically tested:

✅ 1. Appearance Test
– Pure lactose should be a white, crystalline powder.
– It should be odorless and slightly sweet in taste.

🔬 2. Solubility Test
– Dissolve in distilled water.
– Should be freely soluble in water and insoluble in alcohol.

🧪 3. Identification Test
– Molisch’s Test: Add a few drops of α-naphthol and concentrated sulfuric acid. A violet ring at the interface confirms the presence of carbohydrates.
– Benedict’s Test: Heat with Benedict’s reagent. No red precipitate should form—indicating absence of reducing sugars like glucose.

⚗️ 4. Purity Tests

a. Test for Reducing Sugars
– Dissolve sample in water.
– Add Fehling’s solution and boil.
– No brick-red precipitate should form—indicating absence of glucose or other reducing sugars.

b. Test for Starch
– Add iodine solution to the sample.
– No blue coloration should appear—indicating absence of starch.

c. Test for Sulfates
– Add barium chloride to acidified solution.
– No white precipitate should form—indicating absence of sulfate impurities.

d. Test for Heavy Metals
– Use sodium sulfide or hydrogen sulfide.
– No coloration should appear—indicating absence of lead or other heavy metals.

📊 5. Loss on Drying
– Heat a sample at 105°C.
– Weight loss should be less than 0.5%, indicating low moisture content.

🧼 6. pH Test
– A 10% solution should have a pH between 4.5 and 6.5.

📘 Reference Standards
– Pharmacopoeia standards (e.g., IP, USP, BP)
– FSSAI Manual of Milk Testing [Manual of Methods – FSSAI]