458 
TESTING FOR ANTIMONY AND ARSENIC. 
ammoniacal nitrate of silver, the ammoniacal sulphate of 
copper, and sulphuretted hydrogen ; and then dilute solution 
of potash boiled in the tube dissolves the remaining oxide of 
antimony, the presence of it in the potash solution being dis- 
coverable by the orange red precipitate again resulting after 
filtering, acidulating, and passing sulphuretted hydrogen. 
Thus far my object was attained, to the extent of being 
able to abandon the use of the permanganate, without substi- 
tuting any other oxidizing salt; but it will be observed that I 
had to make two heating operations — one, the heating of the 
dry coated copper, and the other, the boiling to dissolve the 
oxide in the alkaline solution. Though two heating ope- 
rations are not particularly objectionable, yet I felt desirous 
of obviating the necessity of more than one ; and a few trials 
showed that the object may be practicably and conveniently 
effected. Thus, copper coated with antimony is put into a 
tube, and a very dilute solution of caustic potash is added.* 
The solution is boiled with the copper in it ; and then the 
tube is so inclined that the copper slips out of the solution (or 
it may be drawn out by a copper wire) into the part of the 
tube where the solution is not, and allowed to remain there 
for a few seconds or a minute or two ; after which it is re- 
turned into the solution (kept boiling hot) for a minute or two, 
when it is again caused to be out of the solution and in the 
air in the tube for a short time. This alternate immersion of 
the copper in the boiling liquid and the exposure of it to the 
air, is frequently repeated till the colour and altered appear- 
ance of the copper inform us that the antimony has been 
oxidized and dissolved off it. The solution is then filtered, 
acidulated with pure hydrochloric acid, and subjected to the 
action of sulphuretted hydrogen gas, when the true orange 
red sulphuret of antimony precipitates, as in the other in- 
stances. By the exposure of the coated copper alternately 
to the hot solution and (while itself warm) to the air, the 
oxidation and solution of the antimony go on rather quickly; 
so much so, indeed, that only from a few minutes to about 
half an hour is required for the solution of the whole of the 
antimony; the length of time, between these limits, varying 
according to the density and quantity of antimony upon the 
copper. 
By the exposure of copper (coated with antimony) made 
wet with cold solution of potash, and exposed to cold atmo- 
* The coated copper must be previously well washed with water, and 
then a solution, 100 grain measures of which have an alkaline action equal 
t/o one third of a grain of potash, is sufficiently strong, when the copper is 
not thickly coated. 
