Magnesium stearate is a loose white powder with a smooth feel. It is insoluble in water, ethanol and ether, but soluble in hot water and ether. It decomposes into stearic acid when exposed to acid. and the corresponding magnesium salts. The solubility in room temperature water is 77-79 mg/L, and it is soluble in hot ethanol. It has a slight odor and a greasy feel.
The analysis method of magnesium stearate content is as follows:
Accurately weigh about 1g of the sample, add 50ml of 0.1mol/L hydrochloric acid, and boil for about 30 minutes, or until the precipitated fatty acid layer is clear. If necessary, add water to the original volume. Cool, filter, and rinse the filter and filter residue with water until the eluate is no longer acidic to litmus.
Neutralize the filtrate with 1mol/L sodium hydroxide solution until the litmus becomes neutral.
Under full stirring with a magnetic stirrer, use 0.05mol/L ED] limited disodium for the following titration: first add 30ml of titrant solution from a 50ml buret. , add 5 ml of ammonia/potassium chloride buffer test solution (TS-12) and 0.15 ml of wool-chrome black test solution (TS-97), and then continue titrating to the blue end point. Each milliliter of 0.05mol/L ED-TA disodium solution is equivalent to MgO2.015mg.
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