ARS 
ing, in which are deposited all kinds of arms, 
and other warlike implements, such as can- 
non, mortars, howitzers, small arms, and 
every other warlike kind of engines and in- 
struments of death. 
ARSENIATES, in chemistry, a genus of 
salts, formed from arsenic acid and some 
particular base ; thus we have the arseniates 
of potash, the arseniates of soda, lime, &c. 
They are distinguished by the following pro- 
perty : when heated with charcoal powder, 
they are decomposed, and the arsenic sub- 
limes. These salts have not hitherto been 
applied to any useful purpose, and have at 
present been but superficially examined. 
ARSENIC, in mineralogy, one of the me- 
tals that are brittle and easily fused.The word 
occurs first in the works of Dioscorides, and 
other authors, who wrote about the beginning 
of the Christian aera: it denotes in their 
works the same substance which Aristotle 
had called o-atSafayy, which is a reddish-co- 
loured mineral, composed of arsenic and sul- 
phur, used by the ancients in painting and 
as a medicine. 
Arsenic, as it is to be found in the 
shops, occurs in the state of a white oxide, 
from which the metal may be obtained by 
the following process. Mix two parts of the 
white oxide with one part of black flux 
(prepared by detonating, in a crucible, one 
part of nitre with two of crystals of tartar), 
and put the mixture into a crucible. In- 
vert over this another crucible ; lute the 
two together, by a mixture of clay and sand, 
and apply a red heat to the lower one. The 
arsenic will be reduced, and will be found 
lining the inside of the upper crucible, in a 
state of metallic brilliancy. Arsenic is oxi- 
dized by mere exposure to the atmosphere. 
It soon becomes tarnished, loses its metallic 
lustre, and is changed into a blackish oxide. 
It is readily fusible, and is volatilized at 
356°. In close vessels it may be collected 
unchanged ; but when thrown on a red hot 
iron, it burns with a blue flame and a white 
smoke, and a strong smell of garlic is per- 
ceived. All the mineral acids act on ar- 
senic ; but not considerably, unless they are 
heated. In the oxigenized muriatic acid 
gas, however, arsenic burns vehemently. A 
mixture of oxy-muriate of potash and ar- 
senic furnishes a detonating compound, 
which takes fire with the rapidity of light- 
ning. The salt and metal, first separately 
powdered, may be mixed by the gentlest 
possible triture, or rather by stirring them 
together on paper with a knife point. If two 
long trains be laid on a table, the one of 
ARS 
gunpowder, and the other of this mixture, 
and they be in contact with each other at 
one end, so that they may be fired at once, 
the arsenical mixture burns with the ra- 
pidity of lightning, while the other burns 
with comparatively extreme slowness. Ar- 
senic has the property of giving a white 
stain to copper. Let a small bit of metallic 
arsenic be put between two small plates of 
copper; bind these closely together with 
iron wire, and heat them, barely to redness, 
in the fire. The inside of the copper plates 
will be stained white. The white oxide of 
arsenic lias the following properties : 1 . It 
has an acrid taste, and is highly poisonous. 
2. It is soluble in water, which, at the ordi- 
nary temperature, take up l-80th. Ac- 
cording to La Grange, it is soluble in l-24th 
of cold water, or 1-I5th of hot. 3. Oxide 
of arsenic combines with the pure alkalies 
to saturation ; and hence it fulfils one of the 
principal functions of an acid. It has there- 
fore been called arsenous acid, and its com- 
pounds arsenites. They may be formed by 
simply boiling the acid with a pure alkaline 
solution. 4. The arsenous acid, by distilla- 
tion with sulphur, affords either a yellow 
substance, called orpiment, or a red one, 
termed realgar. Both these compounds 
are sulphuretted oxides of arsenic, varying 
in the proportion of their components. The 
hydj'o-sulphurets also throw down a yellow 
precipitate from solutions of arsenous acid. 
Sulphate of copper, mixed with arsenite 
of potash, gives a beautiful precipitate, call- 
ed, from its discoverer, Scheele’s green. 
5. By repeated distillation with nitric acid, 
arsenous acid is changed into arsenic acid. 
The same change is effected also by expo- 
sure to the vapour of oxigenized muriatic 
acid, and the expulsion, by heat, of the com- 
mon muriatic acid. By both these pro- 
cesses, a white concrete substance is ob- 
tained, termed arsenic acid. The arsenic 
acid has a sour, and at the same time, a me- 
tallic taste. It reddens vegetable blues, at- 
tracts humidity from the atmosphere, and 
effervesces strongly with solutions of alka- 
line carbonates. With alkalies, earths, and 
oxides, it constitutes a class of salts, called 
arsenates. The arsenate of potash may be 
obtained in a more simple manner, by deto- 
nating, in a crucible, a mixture of nitrate 
of potash with arsenous acid. When tin is 
dissolved in arsenic acid, an inflammable 
gas is disengaged, as was observed by 
Scheele, consisting of hydrogen gas, holding 
arsenic in solution. It may be obtained 
also by adding powdered metallic arsenic to 
