546 
RESEARCH FOR ARSENIC AND ANTIMONY. 
only substance deposited in a form to be mistaken for arsenic 
is antimony. The other substances present no difficulty what* 
ever. Their colour, and their other physical properties, as 
well as the absence of any crystalline sublimate on heating 
to about 400° the deposit obtained by heat, at once dis¬ 
tinguishes them from arsenic. The deposit produced by 
heat from the hydrogen-compound of antimony, is blacker 
than that procured from arsenic; and if air is not entirely ex¬ 
cluded at the time of heating the tube, some oxide, of a 
grayish-white colour, is at the same time deposited. The 
antimonial deposit is known from that of arsenic by its re¬ 
quiring a high temperature for sublimation, and by its not 
producing octahedral crystals. It is simply converted to a 
white amorphous oxide, at a higher temperature than the 
arsenical deposit requires for its sublimation. If a sufficient 
quantity of oxide is obtained in the form of a sublimate, this 
may be dissolved in a solution of pure tartaric acid, and the 
antimony precipitated from this solution, as an orange-red 
sulphide, by a washed current of sulphuretted hydrogen gas. 
The crystalline sublimate from arsenic can be driven by 
heat to various parts of the tube ; the amorphous deposit of 
antimony is fixed. Finally, these metals are entirely sepa¬ 
rated and distinguished from each other in the third stage. 
The antimoniuretted hydrogen received into strong nitric 
acid is converted into antimonious or antimonic acid, which 
is left as a white, non-deliquescent residue by evaporation of 
the acid. This residue is quite insoluble in water and alco¬ 
hol ; and thus any arsenic acid mixed with it may be sepa¬ 
rated from it by digesting the residue in watery alcohol, and 
filtering the liquid. If tested by nitrate of silver, in the 
capsule in which it is collected, no red-coloured precipitate is 
produced , but on adding a drop of ammonia, black antimo- 
nide of silver is immediately formed. The passage of anti¬ 
moniuretted hvdrogen into a solution of nitrate of silver 
causes the precipitation of the whole of the silver as a black 
antimonide. The filtrate precipitated by hydrochloric acid 
gives no precipitate with a current of sulphuretted hydrogen. 
By either of these methods, therefore, arsenic and antimony 
are discovered in traces, are known from each other, and can 
be separated from each other. 
Arsenic acid and the alkaline arseniates, as well as the sul¬ 
phide of arsenic, are not easily obtained in the form of chlo¬ 
ride of arsenic by the distillation process. Some portion 
passes over as chloride of arsenic, but much remains un¬ 
changed in the retort. Arsenious acid and the arsenites, 
soluble and insoluble in water, are most readily obtained in 
