White alum is made by processing and refining the sulfate mineral alunite. Mainly containing hydrated potassium aluminum sulfate, this product is in irregular block or granular shape. Colorless or light yellowish white, transparent or translucent. The surface is slightly smooth or uneven, with fine longitudinal ridges and a glass-like luster. Hard and brittle. The smell is slight, the taste is sour, slightly sweet and extremely astringent.
[Identification] The aqueous solution of this product shows the identification reaction of aluminum salt, potassium salt and sulfate.
[Check] Ammonium salt: Take 0.1g of this product, add 100m1 of ammonia-free distilled water to dissolve, take 10m1, put it in a colorimetric tube, add 40ml of ammonia-free water and 2m1 of alkaline potassium mercury iodide test solution, if color develops, mix with chlorine The mixture of 1m1 ammonium chloride solution, 2m1 alkaline potassium mercury iodide test solution and 49m1 ammonia-free distilled water should not be deeper.
Copper salt and zinc salt: Take 1g of this product, add 100m1 of water and a slight excess of ammonia test solution, boil and filter. The filtrate should not appear blue. After adding acetic acid to the filtrate to make it acidic, add hydrogen sulfide test solution. No oxidation will occur. turbid.
Iron salt: Take 0.35g of this product, add 20m1 of water to dissolve, add 2 drops of nitric acid, boil for 5 minutes, add sodium hydroxide test solution dropwise to neutralize until slightly turbid, add 1m1 of dilute hydrochloric acid and 1m1 of potassium ferrocyanide test solution Mix appropriate amount of water to make 50m1, shake well, no blue color should appear within 1 hour.
Heavy metals: Take 1g of this product, add 2m1 of dilute acetic acid and an appropriate amount of water to dissolve it into 25m1. Check according to the law and the heavy metal content should not exceed 20mg/kg.
