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.

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    or three minutes to the flame, a little cyanide of potassium may be added, and the experiment continued for two or three minutes longer. Many of the metallic arsenides and sulphides require to be carefully roasted, and thus deprived of their arsenic and sulphur, and the metals themselves oxidized, before they can be reduced by carbonate of soda ; in this case the residue which remains from the open-tube experiment can be employed. It must be remembered, however, that cadmium as well as sulphur and arsenic may have been expelled by the roasting. 7 562. The metals which can be reduced by this means, besides gold, platinum, and silver, are lead, antimony, tin, copper, zine, bismuth, nickel, cobalt, iron, cadmium, arsenic, and mercury. “Gold, silver, copper, and tin compounds yield metallic beads, but no incrustations; iron, nickel, cobalt, and platinum compounds give neither beads nor in- crustations; bismuth, lead, and cadmium compounds produce a yellow or brown deposit on the charcoal: antimony and zinc give a white incrustation;* arsenic may easily be recognised by its odour.” 563. If a globule has been obtained, it is necessary to ascertain whether it is malleable or brittle: “for this pur- pose, it is allowed to cool perfectly, and carefully removed with a pair of tweezers. Having been placed upon the anvil, and struck with the hammer—or, if these two blow- pipe instruments are not at hand, upon the bottom of a strong mortar—and struck sharply with the pestle, when, if brittle, it of course falls to powder (as in the case of anti- mony); if semi-malleable, it flattens out, at the same time breaking into several pieces (as with bismuth); and if fully malleable, flattens out without breaking (like lead). * It must be remembered that charcoal becomes, on exposure to the blowpipe flame, covered with a bluish-white ash.