How to check Magnesium carbonate

Magnesium carbonate is a kind of white granular powder; odorless, almost tasteless. Magnesium carbonate is almost insoluble in water, but can make the water into a weak alkaline, not soluble in ethanol, can bubble dissolved in dilute acid.

The classical differential method：

Take proper amount of magnesium carbonate (CAS NO: 13717-00-5), with dilute hydrochloric acid or bubble dissolution, reaction solution of magnesium salt (Chinese Pharmacopoeia 1995 two Appendix III).

Chloride identification：

Taking 0.2g magnesium carbonate, plus nitric acid 0.4ml and the amount of water to dissolve, to check the (Chinese Pharmacopoeia 1995 edition two appendix VIII A), compared with the standard was prepared from sodium chloride solution 7.0ml, not more concentrated (0.035%).

Sulfate identification：

Taking magnesium carbonate with hydrochloric acid 0.1g, 1ml and amount of water dissolved, diluted with water to 25ml, then 10ml solution, according to inspection (Chinese Pharmacopoeia 1995 two appendix VIII B), compared with standard potassium sulfate solution was prepared from 3.0ml, and not more concentrated (0.75%).

Calcium oxide identification：

Taking magnesium carbonate is about 1g, accurately weighed, according to method of magnesium oxide under the (Chinese Pharmacopoeia 1995 two 733 pages containing calcium oxide) examination, shall not exceed 0.6%.

Soluble salts identification：

Taking 1g magnesium carbonate, add 50ml of water, boil 5 minutes, filtration, the filtrate is evaporated to dryness on the water bath, and drying at 105 deg.c for 1 hours, remaining residue shall not be too 10mg.

Identification of hydrochloride：

Taking 2g magnesium carbonate, add 75ml of water, then add a small amount of hydrochloric acid with time, added with stirring, to no longer dissolved, boil for 5 minutes, filter, filter residue is washed with water to wash, no significant response to chloride, ignition to constant weight, remaining residue shall not be too 2mg.

Iron identification：

Taking 0.25g magnesium carbonate, diluted nitric acid 5ml, boil for 1 minutes, let cool, dilute with water to 35ml, to check the (Chinese Pharmacopoeia 1995 edition two appendix VIII G), compared with standard iron solution was prepared from 5.0ml, shall not be deeper (0.02%).

Identification of heavy metals：

Taking 0.5g magnesium carbonate with dilute hydrochloric acid, 5ml and 10ml of water, boil 5 minutes, cooling, filtration, the filtrate with phenolphthalein indicator solution 1 drops of ammonia solution to the solution and amount of light red, light and acetate buffer (pH3.5) 2ml and the amount of water to 25ml, 0.5g and ascorbic acid, dissolved, inspection in accordance with law (Chinese Pharmacopoeia 1995 edition two appendix VIII H first law), placed 5 minutes than color, containing heavy metals shall not exceed thirty ppm.

Identification of arsenic salt：

Taking 0.4g magnesium carbonate with hydrochloric acid, 5ml and water 23ml, dissolved, according to inspection (Chinese Pharmacopoeia 1995 two appendix VIII J first law), should accord with the regulations (0.0005%).

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