TESTING FOll ANTIMONY AND ARSENIC. 
457 
which time it had acquired a dark-coloured or soot-like coat- 
ing of or containing antimony ; for, when the zinc so coated 
was put into Marsh’s apparatus with pure diluted sulphuric 
acid, the gas produced gave deposits of metallic antimony, not 
soluble by the application of chloride of lime. The result of 
this experiment was a valuable corroboration of the results, 
indicative of antimony from the other experiments. 
Dr. Odling’s process, published since the trial of M‘Mullen, 
consists in first boiling the coated copper in solution of per- 
manganate of potash with a little excess of potash for a few 
minutes, by which the antimony becomes oxidized, and the 
oxide is dissolved by the excess of alkali ; then filtering the 
solution, slightly acidulating it, and passing sulphuretted 
hydrogen gas through it; the truly characteristic orange red 
precipitate being thereby produced, w 7 hich may be collected 
and further tested in the usual manner. It will be perceived 
how r much more directly the orange precipitate is obtained by 
this process than by that I had to adopt in M‘Mullen’s case. 
As Dr. Odling remarks, one ebullition, one filtration, and one 
reaction, are all that are required for the complete identifica- 
tion of the antimonial deposit; that is, so far as it can be 
identified merely by the orange-red precipitate. But, as it is, 
of course, requisite to test the purity of the potash and of the 
permanganate of potash used, so as to see that they do not 
contain antimony, it occurred to me that an advantage would 
be gained if one of these ingredients could be dispensed with, 
if the antimony could be oxidized, and the oxide dissolved in 
solution of potash, without the aid of permanganate of potash 
or any other salt. Accordingly, I introduced some copper 
having antimony deposited upon it into a subliming or reduc- 
tion tube, and then heated to redness that part of the tube 
where the copper was ; the usual white amorphous oxide was 
formed and deposited in the tube. I then took the copper 
out of the tube, and poured in a very dilute solution of 
caustic potash. On boiling this solution of potash, the oxide 
soon became dissolved. I then filtered the solution, acidulated 
it with pure hydrochloric acid, and passed sulphuretted 
hydrogen gas, obtaining the true orange red precipitate of 
sulphuret of antimony. I have repeated the experiment many 
times with the same success ; and I have further found that, 
when copper, having a mixture of antimony and arsenic 
deposited upon it, is similarly heated in the subliming tube, it 
is easy to prove the presence of both metals in the sublimate 
formed ; for instance, distilled water boiled in the tube, re- 
peatedly, dissolves the arsenious acid from the oxide of anti- 
mony, arsenious acid being discoverable in the solution by the 
xxx. 6 1 
