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 . Fig. 37. Fig. 38. Examination: Fixed impurities are recognized by a residue after completeevaporation of a few drops of the acid upon platinum-foil. Lead is indicated by a white turbidity taking place upon thecareful
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 . Fig. 37. Fig. 38. Examination: Fixed impurities are recognized by a residue after completeevaporation of a few drops of the acid upon platinum-foil. Lead is indicated by a white turbidity taking place upon thecareful admixture of one part of the acid with about four orfive times its volume of alcohol (Fig. 37). Another methodof readily recognizing the presence of lead in sulphuricacid is, to fill a small conical cylinder about half with con-centrated hydrochloric acid, and then to place below the acid,by means of a pipette, a nearly equal volume of the sulphuricacid, with care that the fluids do not mix (Fig. 38); an ensuingwhite turbidity at the junction of the two fluids would confirmthe presence of lead. 106 MANUAL OF CHEMICAL ANALYSIS. The presence of lead and other metallic impurities may bealso detected by nearly neutralizing the acid, diluted with twoor three times its bulk of water, with aqua ammonise or liquorpotassse, and by adding, while yet warm, an equal volume of. Fig. 89. hydrosulphuric acid, and allowing the liquid to stand fur sev-eral hours ; a precij^itate would indicate lead or other metals,which, when required, may be further examined by the meth-ods described in the course of analytical investigation (page41). ACID A. 1Q7 Arsenic may be detected by either of the two followingmethods: 1. About half a fluidounce of a mixture of equal parts, byvolume, of the concentrated sulphuric acid and water is,when cool, heated in a test-tube, and a solution of potassiumpermanganate added drop by drop, until decoloration ceases;then about 20 grains of sodium chloride, and subsequent
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