Laboratory manual for the detection of poisons and powerful drugsAuthorized translation of the completely rev4th German ed. . s silver phosphide becausethis compound is partially decomposed by water. Phosphoric and phosphorousacids pass into solution: (a) 2Ag3P + 5O + 3H2O = 6Ag + 2H3PO4, (b) 2Ag3P + 3O + 3H2O = 6Ag + 2H3PO3. 10 DETECTION OF POISONS If there is silver phosphide in the precipitate, the filtrate willcontain phosphoric or phosphorous acid (see Note, page 9).To detect phosphoric acid, first add hydrochloric acid to removeexcess of silver from this filtrate. Filter through paper pr
Laboratory manual for the detection of poisons and powerful drugsAuthorized translation of the completely rev4th German ed. . s silver phosphide becausethis compound is partially decomposed by water. Phosphoric and phosphorousacids pass into solution: (a) 2Ag3P + 5O + 3H2O = 6Ag + 2H3PO4, (b) 2Ag3P + 3O + 3H2O = 6Ag + 2H3PO3. 10 DETECTION OF POISONS If there is silver phosphide in the precipitate, the filtrate willcontain phosphoric or phosphorous acid (see Note, page 9).To detect phosphoric acid, first add hydrochloric acid to removeexcess of silver from this filtrate. Filter through paper pre-viously well washed with acid and water and completely expelhydrochloric acid from the filtrate by evaporation upon thewater bath with concentrated nitric acid. Dissolve the resi-due in a little warm water and test for phosphoric acid with am-monium molybdate or magnesia mixture. 2. Examination of the Silver Precipitate (AgsP) for Phos-phorus.—Two forms of apparatus may be used for this purpose,namely: (a) Fresenius-Neubauer^ Apparatus.—Generate hydrogenin flask A (Fig. 4) from pure phosphorus-free zinc and dilute. Fig. 4.—Fresenius-Neubauer Apparatus. sulphuric acid. Fill U-tube C with pieces of pumice stone satu-rated with concentrated potassium hydroxide solution to ab-sorb any hydrogen sulphide. Use hard glass for tube D and ^ C. R. Fresenius, Qualitative chemische Analyse, XVI edition, page 521. VOLATILE POISONS 11 have the tip F of platinum. The part marked E^ is a glassstop-cock or screw-tap. Reservoir B serves to hold liquid fromA when cock E is closed. A platinum tip is essential, other-wise the flame instead of being colorless will always be yellowfrom sodium in the glass. The place where the platinum tip isfused into the glass should be cooled by wrapping cotton aroundthe glass and keeping it moist. Procedure.—Open E and let hydrogen from A pass for sometime through the apparatus to expel air. Then close E andliquid in A will rise into B. Now open E just en
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