38 
RESEARCH FOR ARSENIC AND ANTIMONY. 
tioned, when nitrate of silver is added to it. 3. Sulphide of 
ammonium does not readily dissolve the deposit, but when 
mixed with it, enough is dissolved to leave, on evaporation, 
yellow sulphide of arsenic (orpiment), soluble in ammonia, 
but insoluble in cold hydrochloric acid. The pale, steel-blue 
colour of the flame, with the production of a white smoke 
(arsenious acid), and the metallic deposits or mirrors, received 
on glass or porcelain, are well-known characters of arseni- 
uretted hydrogen gas in a state of combustion. 
It has been suggested that the copper or silver tests might 
be applied to the products by moistening surfaces of glass 
with the respective solutions, and holding them at a short dis¬ 
tance above the flame, so that the arsenious acid evolved 
during combustion might be received upon them. 
It is well known that Antimony combines with hydrogen, 
and that this gas, when burnt, produces deposits resembling 
those of arsenic. These may be collected in porcelain cap¬ 
sules, and tested by the method above described. 1. Strong 
Nitric acid dissolves the deposit. On evaporation to dryness, 
a white, insoluble compound is left (an insoluble oxide of 
antimony). Nitrate of silver added to this white residue pro¬ 
duces no change, unless there was arsenic combined with the 
antimony, in which case a spot of red arseniate of silver will 
appear. If to the colourless mixture of oxide of antimony 
and nitrate of silver, a small quantity of ammonia be added, 
or the stopper of a bottle containing ammonia be brought 
near, the residue in the capsule is immediately blackened, 
owing to the production of an insoluble compound of anti¬ 
mony and silver. 2. A strong solution of Chloride of lime 
does not readily dissolve the antimonial deposit. Even when 
heated on a sand-bath, there is no change, and the dry resi¬ 
due gives no red precipitate when treated with nitrate of 
silver. 3. Sulphide of ammoriium readily dissolves the anti¬ 
monial deposit; and on evaporation, red sulphide of antimony 
remains in the capsule, insoluble in ammonia, but easily dis¬ 
solved by cold hydrochloric acid. Antimonial deposits are 
thus easily known from those of arsenic. 
The flame of antimoniuretted hydrogen is of a pale, yellow¬ 
ish-white colour. It furnishes black or smoky-looking de¬ 
posits on glass or porcelain, which are remarkably different 
from the metallic-looking and brown-coloured deposits of 
arsenic. The white oxide of antimony, evolved by combus¬ 
tion, does not produce in the liquid tests for arsenic, held 
above the flame and within the vapour, any coloured preci¬ 
pitates. The ammonio-nitrate of silver is simply blackened 
as a result of the reduction of the metal. 
