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 . necessary, and a portion of ittested with one or two drops of concentrated sulphuric acid;if a white precipitate, indicating the presence of lead, occurs,the larger part of the liquid, or the whole of it, is precipit
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 . necessary, and a portion of ittested with one or two drops of concentrated sulphuric acid;if a white precipitate, indicating the presence of lead, occurs,the larger part of the liquid, or the whole of it, is precipitatedwith sulphuric acid ; the precipitate is washed with water bycareful decantation, and then agitated for 10 minutes withtepid liquor potassse; the liquid is then passed through a moistfilter, and the filtrate mixed with an equal volume of hydrosul-phuric acid; a black precipitate will confirm the presence of lead. Copper salts are detected, in the diluted nitric-acid solution11 162 MANUAL OF CHEMICAL ANALYSIS. of the bismuthoTis nitrate, by a reddish-brown precipitate withpotassium ferrucjanide. Arsenic may surely enough be recognized by its character-istic odor, when a mixture of five grains of the bismuthousnitrate with 10 grains of powdered potassium bitartrate is in-cinerated, either in an iron spoon or in a small cavity uponcharcoal, before the blow-pipe (Fig. 50).. Fig. 50. As an additional or confirmatory evidence of the absenceor presence of arsenic, either of the two following tests may beapplied : About 20 grains of the bismuthous nitrate are addedto about two fluid-drachms of concentrated sulphuric acid, in atest-tube or in a small flask, and the mixture boiled ; the tubeor flask is held, as much as practicable, in an inclined position,so as to allow the nitric and nitrous acid vapors to escape ;when the evolution of such vapors ceases, two fluid-drachms ofconcentrated hydrochloric acid are added, and the mixture isallowed to cool, and may serve, in two separate p
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