70 
is a brilliant metallic, but occasionally it has a greyish 
tarnish. The hardness = 5*5—6*0, so that it gives sparks 
with the steel, while at the same time the arsenical odour 
may be perceived. The fracture is uneven and it may 
be easily reduced to powder. 
The elements are bi-arseniuret of iron and bi-sulphuret 
of iron Fe S 2 + Fe As 2 . It frequently contains silver. On 
charcoal it gives off arsenical fumes, and melts readily to 
a metallic globule. With soda it gives flour of sulphur. 
When heated in a tube red sulphuret of arsenic is sublimed, 
and afterwards some metallic arsenic, and grey sulphuret 
of iron remains as residue. 
There is a sulphurless arseniuret of iron of similar 
crystalline relations, colour, and appearance, which may be 
distinguished by its greater weight (7*2—7*3). It is a bi- 
arseniuret of arsenic, which sublimes metallic arsenic in the 
retort, and does not give flour of sulphur with soda. This 
variety occurs at Reichenstein, in Silesia and Schladming, 
in Styria ; the other is much more abundant, and is found 
especially at the Erzgebirge and the Harz. 
Fig. 18.— Arsenious Acid, White Arsenic. 
This is found in regular octahedrons of adamantine 
lustre, Fig. 18; occasionally also in tetrahedrons, acicular, 
and as an earthy or crystalline efflorescence. Colourless, 
of 3*0 hardness, and 3*6—3*7 specific gravity. The crystals 
consist of pure arsenious acid As, composed of two equiva¬ 
lents of arsenic (= 75*81) and three of oxygen (= 24*19). 
It volatilises on the charcoal, giving off its peculiar odour, 
and sublimes in the retort. It is soluble in water; the 
solution gives a golden yellow precipitate with sulphuretted 
hydrogen, which is again soluble in caustic ammonia. 
It is found in small quantity, generally as a product of 
decomposition, or of the action of fire, arising from other 
arsenical ores, at Bieber in Hesse, Andreasberg, Mariakirch, 
etc. Much finer crystals are formed in roasting many of 
the ores of arsenic. It is the most active poison of the 
mineral kingdom, but is mostly produced artificially, and 
is then brought into commerce as white arsenic. 
Figs. 19 and 20.—Pharmacolite, Arseniate of Lime. 
Crystallises in oblique rectangular prisms, which, how¬ 
ever, are for the most part combined with truncation of the 
lateral and basal edges, as Fig. 19. It also occurs radiately 
foliated, capillary, in bundles, botryoidal, or as a pulveru¬ 
lent encrustation, like Fig. 20. White passing into reddish, 
occasionally coloured peach-blossom-red by arseniate of the 
oxide of copper, of pearly lustre, translucent, of 1*0—1*5 
hardness and 2*4—2*6 specific gravity. The composition 
is simple arseniate of lime, with six equivalents of water. 
In the retort it gives off water, and when melted distributes 
on the charcoal arsenical fumes and a residue of white 
encrustation. It is soluble in nitric acid without effer¬ 
vescence, and is insoluble in water. There is also a mag¬ 
nesian pharmacolite of similar appearance, which has been 
called jpicrojpharmacolite. The latter is found at Reichers- 
dorf in Hesse, the former at the Schwarzwald, the Harz, 
Erzgebirge, etc., finest in old mines, where the lode contains 
calcite, as a product of decomposed cobalt ores, containing 
arsenic. 
