Manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Manual of qualitative analysis / by Robert Galloway. Source: Wellcome Collection.

    186/272 (page 168)
    nitric acid. If this precipitate, after being dried, is heated in the outer flame of the blowpipe, it becomes distinctly crystalline on cooling. This test is very characteristic, not only on account of the crystalline structure of the bead, but also from the circumstance that the phosphate of lead is the only salt of that metal which is not reduced to the metallic state when heated in the inner blowpipe flame. It is evident that, to render this test of any value, the phosphate of lead must be freed thoroughly, by washing, from all acetate of lead. 424. Mitrate of silver throws down, both from solutions of phosphates containing one or two atoms of fixed base, as well as from phosphates containing three atoms of fixed base, a light yellow precipitate of phosphate of silver (3 AgO, PO,), which is readily soluble in nitric acid and in ammonia. If the solution contained a phosphate contain- ing three atoms of fixed base, the fluid in which the preci- pitate is suspended will manifest a neutral reaction, whilst the reaction will be acid if the solution contained a phos- phate containing one or two atoms of fixed base. The acid reaction is occasioned by the nitric acid receiving, for the three equivalents of oxide of silver which it yields to the phosphoric acid, only 2 or 1 eq. of fixed base, and 1 or 2 en: of water; and as the latter does not neutralize the acid properties of the nitric acid, the solution becomes acid. Monobasic and bibasic phosphate of silver is white; conse- quently, a tribasic phosphate, containing 1 or 2 eq. of fixed base, yields, after ignition, a white precipitate with nitrate ‘of silver (AgO, PO,, or 2 AgO, PO,). 425. “If toa solution containing phosphoric acid and the least possible excess of hydrochloric or nitric acid a tolerably large amount of acetate of soda is added, and then a drop of sesquichloride of iron, a yellowish-white flocculent- gela-