MEDICO-LEGAL CONTRIBUTIONS ON ARSENIC. 571 
and if then it is held inclining upwards in the flume of an 
alcohol lamp, the flame will be tinged bluish-wdiite, and the 
characteristic garlic odour may be perceived. 
c. Gui/’s method of reduction, —As it is often difficult to 
distinguish the octahedral form of the arsenious acid crystals, 
or critically to examine the deposits, when the quantity is 
small and contained in a tube, Guy proposes the following 
method ; 
A tube is employed three-fourths of an inch in length, 
and of rather larger diameter than is commonly employed. 
This tube is supported in a vertical position by being dropped 
into a hole punched in a slip of copper foil. The arsenical 
mixture is then dropped into the tube, and heat carefully 
applied to the closed end; at the same time a clean mi¬ 
croscopic glass cover or a glass slide is placed over the open 
end of the tube. Crystals of arsenious acid are thus pro¬ 
duced, which may readily be examined by the microscope. 
When metallic arsenic is sublimed, the crust is found to 
consist of a multitude of globular particles, or if partially 
oxidized, of octahedral crystals mixed with the globules. 
The delicacy of this test is such, that with the of a 
grain of arsenic thousands of distinct octahedral crystals of 
arsenious acid may be obtained. [Archives of Medicine, No. 
3, p. 2o.) 
d. Oxidation test. —If the closed end of the tube be cut off 
and the mirror is carefully and gradually heated, the arsenic 
will volatilize, and oxidizing becomes converted into arse¬ 
nious acid, which will condense in the cooler part of the tube 
in a mass of minute octahedral crystals. 
e. Solution. —If that part of the tube containing the crys¬ 
talline deposit be heated in a test tube with water the deposit 
will dissolve. With this solution the liquid tests may be 
made as follows: 
Liquid tests. — a. If to the solution a few drops of nitrate 
of silver are added, and then very dilute ammonia, drop by 
drop, the characteristic yellow precipitate of arsenite of silver 
will be produced. 
b. Treated with solution of sulphate of copper and am¬ 
monia, added as above, a grass-green precipitate of arsenite 
of copper will be produced. 
c. Treated with chlorydric acid, and then strong sulphydric 
acid water be added, a precipitate of the yellow sulphide of 
arsenic is produced, soluble in ammonia. 
d. If a small mass of the crystals (see d) be boiled with 
nitric acid, arsenic acid is produced, which gives, with nitrate 
of silver and ammonia added as above, a reddish-brown pre* 
cipitate of arsenite of silver. 
