Calcium stearate is a white powder, insoluble in water, cold ethanol And ether, soluble in hot benzene, benzene and turpentine and other organic solvents, slightly soluble in hot ethanol and ether. It decomposes slowly when heated to 400°C and is flammable. It decomposes into stearic acid and corresponding calcium salts when exposed to strong acid and is hygroscopic. The following will help you understand the identification methods of calcium stearate and heavy metal detection methods:
1. The identification methods of calcium stearate are as follows:
(1) Take about 25g of this product, add 60ml of dilute sulfuric acid and 200ml of hot water, heat and stir frequently to separate the fatty acids into an oil layer, wash the oil layer with boiling water until the washing liquid does not show sulfate reaction, collect the oil layer in a small In a beaker, warm on a steam bath until the oil layer and water layer are completely separated and become transparent, let cool, discard the water layer, heat to melt the oil layer, filter while hot, place in a dry beaker, and dry at 105°C 20 minutes. Determine the freezing point according to the law (General Rule 0613), it should not be lower than 54°C.
(2) Take 1.0g of this product, add 25ml of water and 5ml of hydrochloric acid, shake well, and heat to separate the fatty acids into an oil layer, let it cool, and take the water layer. The water layer will show the identification reaction of calcium salts. (General 0301).
2. The heavy metal detection of calcium stearate is as follows:
Take 2.5g of this product and place it in an evaporating dish as a test tube. Take another 0.5g of this product and place it in another evaporating dish as a reference tube. Add 5 ml of 25% magnesium nitrate ethanol solution respectively, cover the evaporating dish with a short-necked funnel, with the neck facing up, heat on the electric hot plate at low temperature for 30 minutes, then heat at medium temperature for 30 minutes, and let cool; remove the funnel and use the reference tube Add 2 ml of standard lead solution with medium precision, burn the evaporating dishes until the sample becomes ashes, let it cool, add 10 ml of nitric acid to dissolve the residue, move the solution into two 250 ml beakers, and add perchloric acid solution (7-10 ml) to each. )5ml, evaporate to dryness, add 2ml of hydrochloric acid to the residue, rinse the inner wall of the beaker with water, evaporate to dryness, rotate the beaker when it is almost dry; add 2ml of hydrochloric acid, repeat the above operation, let it cool and add about 10ml of water to dissolve the residue; Add 1 drop of phenolphthalein indicator solution to each, neutralize with sodium hydroxide test solution until pink appears, add dilute hydrochloric acid until colorless; add 1 ml of dilute acetic acid and a small amount of activated carbon to each, mix, filter, and place the filtrate in 50 ml of Nessler’s Ratio In the color tube, rinse the filter residue with water and dilute it to 40 ml. Add 1.2 ml of thioacetamide test solution and 2 ml of acetate buffer (PH3.5) each, shake well, let it sit for 5 minutes, place it on white paper, and remove from the tube. When viewed from above and below, the color displayed in the test tube must not be darker than that in the control tube. Containing heavy metals shall not exceed 10 parts per million.
微信扫一扫打赏
