Manual of chemical analysis as applied to the examination of medicinal chemicals : a guide for the determination of their identity and quality, and for the determination of their identity and quality, and for the detection of impurities and adulterations : for the use of pharmaceutists, physicians, druggists, and manufacturing chemists, and of pharmaceutical and medical students . ntly faintly withpotassium permanganate, and by gently heating it. SuljphuriG and hydrochloric acid may be detected by test-ing separate portions of the diluted acid with barium nitratefor the former, and with argent
Manual of chemical analysis as applied to the examination of medicinal chemicals : a guide for the determination of their identity and quality, and for the determination of their identity and quality, and for the detection of impurities and adulterations : for the use of pharmaceutists, physicians, druggists, and manufacturing chemists, and of pharmaceutical and medical students . ntly faintly withpotassium permanganate, and by gently heating it. SuljphuriG and hydrochloric acid may be detected by test-ing separate portions of the diluted acid with barium nitratefor the former, and with argentic nitrate for the latter. Sulphicrous acid is indicated by a greenish coloration, whena little of the acid is heated with a few drops of solution ofpotassium bichromate; it may also be recognized when a mix-ture of about one drachm of the acid wdth two drachms ofdiluted hydrochloric acid and two drachms of water, is pouredupon a little pure granular zinc in a large test-tube, and themouth of the tube is at once loosely closed with a bunch of 72 MANUAL OF CHEMICAL ANALYSIS. cotton moistened with solution of plumbic acetate (Fig. 29);if sulphurous acid be present, the plumbic solution will becomedark, or black. Nitric acid may be detected by discoloration when a littleof the acid is tinged slightly blue with one drop, or part of adrop, of neutral indigo-solution and Fig. 29. Metallic impurities are detected by mixing the acid withabout two or three times its bulk of hydrosulphuric acid, or,when diluted acid is under examination, by saturating it withhydrosulphuric-acid gas, and allowing the liquid to stand ACIDA. 73 in a corked test-tube in a warm place for several, hours ; an en-suing white precipitate would indicate tin or zi7iG (if no sul-phurous acid be present, which also causes a white turbiditywith the reagent), a black one lead or copper j in the latter case,the precipitate may be collected and washed upon a filter, andthen dissolved in a few drops of warm, stro
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