A translation of the Pharmacopoeia of the Royal College of Physicians of London, 1836 : with notes and illustrations / by Richard Phillips.

Royal College of Physicians of London.

Date:: 1838

Credit: A translation of the Pharmacopoeia of the Royal College of Physicians of London, 1836 : with notes and illustrations / by Richard Phillips. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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$purity. If the magnesia contained lime, it would be precipitated from the solution by the bicarbonate of potash; and if insuf- ficiently washed, the sulphate and carbonate of soda which it might contain would be precipitated by the chloride of barium. It acts but slightly on turmeric paper even when moistened. MAGNESiiE Carbonas. Carbonate of Magnesia.—The water in which it is boiled does not alter the colour of turmeric ; chloride of barium or nitrate of silver added to the water does not precipitate anything. One hundred parts dissolved in dilute sulphuric acid lose SQ'^^ parts in weight. When the effervescence has ceased, bicarbo- nate of potash does not precipitate anything from this solution. Remarks.—If the water in which it is boiled alter turmeric, excess of carbonate of soda has been used, and the carbonate of magnesia has not been sufficiently washed. If chloride of barium give a precipitate in the water, then either carbonate of soda or sulphate of soda, or both, may be present from insufficient wash- ing ; and a precipitate yielded by nitrate of silver, insoluble in nitric acid, would indicate the presence of a chloride. The loss of 36*6 per cent, in weight by dissolving it in dilute sulphuric acid, is derived from the expulsion of carbonic acid. Bicarbonate of potash does not precipitate magnesia from sulphuric acid ; if, therefore, there be any precipitate on mixing them, it is derived from impurity. Magnesi^e Sulphas (crystalli). Sulphate of Magnesia {crystals).—Very readily dissolved by water. Sulphuric acid dropt into the solution does not expel any hydro- chloric acid. One hundred grains dissolved in water and mixed with a boiling solution of carbonate of soda, yield 31 grains of carbonate of magnesia when dried. Remarks.—-The non-emission of hydrochloric acid on the addi- tion of sulphuric acid, shows that no notable quantity of any chlo- ride is present. If 34 grains of dry carbonate of magnesia be obtained, the sulphate of magnesia is unmixed with sulphate of soda. Marmor. Marble.—White, dissolves in hydrochloric acid with effervescence. Ammonia throws down nothing from this solution, nor is it decomposed by the addition of a solution of sulphate of lime in water. Remarks.—If ammonia throw down anything from the solu- tion after boiling, it must be an impurity, for lime is not precipi- tated by it. If solution of sulphate of lime give a precipitate, it$