Draft Quality Standard for Kaolin
【Description】
1.1 This product is a white or off-white powder.
1.2 It is almost insoluble in water, dilute acids, or sodium hydroxide solution.
2.【Identification】
2.1 Place about 1g of the product in a porcelain evaporating dish, add 10ml of water, slowly add 5ml of sulfuric acid, mix well, heat until nearly dry, continue heating until white fumes appear, cool, slowly add 20ml of water, and boil for 2-3 minutes. Filter, and the residue is gray. Perform the identification test for aluminum salts according to the "Standard Operating Procedure for General Identification Tests" (HY-STE001) using the filtrate.
3.【Tests】
3.1 Acidity or alkalinity: To 1.0g of the product, add 20ml of water, shake for 2 minutes, filter, take 10ml of the filtrate, add 0.1ml of phenolphthalein indicator solution—the solution should be colorless; when titrated with sodium hydroxide titrant (0.02mol/L) until the solution turns pink, the consumption of sodium hydroxide titrant (0.02mol/L) should not exceed 0.25ml.
3.2 Chloride: To 0.20g of the product, add 25ml of water and 1 drop of nitric acid, boil for 5 minutes, filter, and perform the test according to the "Standard Operating Procedure for Chloride Test" (HY-STE004) using the filtrate. Compare with a control solution prepared from 6.0ml of standard sodium chloride solution; the color should not be deeper (0.03%).
3.3 Sulfate: To 0.30g of the product, add 40ml of water and 2ml of dilute hydrochloric acid, heat to boil for 5 minutes, cool, filter, and perform the test according to the "Standard Operating Procedure for Sulfate Test" (HY-STE005) using the filtrate. Compare with a control solution prepared from 3.0ml of standard potassium sulfate solution; the turbidity should not be greater (0.1%).
3.4 Carbonate: To 1.0g of the product, add 10ml of water and 5ml of hydrochloric acid, mix well—no bubbles should be produced.
3.5 Substances soluble in acid: To 1.0g of the product, add 50ml of hydrochloric acid solution (1→1000), boil for 5 minutes, filter, evaporate the filtrate to dryness, and ignite to constant weight at 500-550°C; the residue should not exceed 10mg.
3.6 Loss on ignition: Ignite 1.0g of the product to constant weight at 550-600°C; the loss in weight should not exceed 15.0%.
3.7 Grit: Place 2g of the product in a beaker, add 50ml of water, stir evenly, pour onto a No. 7 sieve pre-moistened with water, rinse the beaker repeatedly with water until all the sample is transferred to the sieve, and rinse the sieve with water.
3.13 Bacterial endotoxins: Perform the test according to the "Standard Operating Procedure for Bacterial Endotoxin Test" (HY-STE028) (Method 1); the endotoxin content should be less than 10 EU per 1g.

Note: The standard operating procedures for testing referred to in this draft quality standard are established in accordance with the general chapters of the Chinese Pharmacopoeia, Part IV (2020 edition).