Iron oxide yellow, yellow powder; No smell, no smell. It is insoluble in water and easy to dissolve in boiling hydrochloric acid. Take about 0.1g of the product, add 5ml of dilute hydrochloric acid, boil and cool, and then the solution shows the identification reaction of iron salt

　　Take 2.0g of soluble substance in water, add 100ml of water, heat it on water bath for 2 hours, filter it, wash the filter residue with a small amount of water, combine filtrate and washing liquid, put it in a evaporation dish with constant weight of 105 ℃ and steam dry, dry it to constant weight at 105 ℃, and leave residue no more than 20mg (1.0%). Take 2.0g of the insoluble substance in the acid, add 25ml hydrochloric acid, heat it in a water bath to dissolve it, add 100ml of water, filter it with No. 4 vertical melting crucible with constant weight of 105 ℃, wash the residue with hydrochloric acid solution (1 → 100) until the washing solution is colorless, then wash it with water to avoid chloride reaction. Dry it to constant weight at 105 ℃ and the residue shall not exceed 20mg (1.0%). Take about 1.0g of the product for weight loss during ignition, weigh it precisely, and burn it to constant weight at 700-800 ℃ and the weight loss reduction shall not exceed 12.0%. Take 0.2g of barium salt, add 5ml hydrochloric acid, heat it to dissolve, add one drop of hydrogen peroxide test solution, add 20ml of 10% sodium hydroxide solution, filter through, wash the filter residue with 10ml of water, combine the filtrate and washing solution, add 10ml of sulfuric acid solution (2 → 10) and do not show turbidity. Take 0.5g of the product and 10ml hydrochloric acid, heat it to dissolve, add 3ml of nitric acid, boil for 1 minute, cool it, shake it with anhydrous ether for 4 times (30m, 20ml, 20ml and 20ml), discard the ether layer, heat and remove the remaining ether in the acid solution. The ammonia test solution is alkaline, add 1ml of potassium cyanide test solution, add water to 50ml, add several drops of sodium sulfide test solution, shake well, if color is shown, Compared with the control solution made by the same method, the standard lead solution 1.5ml should not be thicker (0.003%). Take 0.2g of arsenic salt, add 7ml hydrochloric acid, heat it to dissolve, add 21ml of water, drop the acid stannous chloride test solution to make the Yellow fade, and check according to law (Appendix VIII J first law), which shall meet the requirements (0.001%).