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A System of Instruction in the Practical Use of the Blowpipe - Being A Graduated Course Of Analysis For The Use Of Students And All Those Engaged In The Examination Of Metallic Combinations by Anonymous
page 53 of 359 (14%)
gas, when in the presence of a metallic oxide, easily reduces the
metal, by withdrawing its oxygen from it, and being changed into
carbonic oxide. If a little fly-stone is mixed with some formiate of
soda, and heated in the bulb, the arsenic is reduced, volatilized, and
condenses in the cool portion of the tube. By this method, the
smallest portion of a grain of the arsenical compound may be thus
examined with the greatest readiness. If the residue is now washed, by
which the soda is got rid of, the metallic arsenic may be obtained in
small spangles. If the compound examined be the sulphide of antimony,
the one-thousandth part can be readily detected, and hence this method
is admirably adapted to the examination of medicinal antimonial
compounds. The arsenites of silver and copper are reduced by the
formiate of soda to their metals, mixed with metallic arsenic. The
mercurial salts are all reduced with the metal plainly visible as a
bright silvery ring on the cool portion of the tube. The chloride and
nitrate of silver are completely reduced, and may be obtained after
working out the soda, as bright metallic spangles. The salts of
antimony and zinc are thus reduced; also the sulphate of cadmium. The
sublimate of the latter, although in appearance not unlike that of
arsenic, can easily be distinguished by its brighter color. It is, in
fact, the rich yellow of this sublimate which has led artists to adopt
it as one of their most valued pigments.


2. EXAMINATIONS IN THE OPEN TUBE.


The substance to be operated upon should be placed in the tube, about
half an inch from the end, and the flame applied at first very
cautiously, increasing gradually to the required temperature. The
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