538 RESEARCH FOR ARSENIC AND ANTIMONY. 
experiments M ere repeated in porcelain capsules, there was 
no residue from the strong acid, but an abundant residue 
from the diluted acid. 
Nearly all the soft organs, including the muscles, contain 
from 60 to 70 per cent, of water; and this furnishes a great 
obstacle to the entire separation of the arsenic by distillation. 
In the analysis of liquids, such as the blood, urine, or vomited 
matters, it is desirable to bring them to dryness by a water- 
bath before treating them with hydrochloric acid. 
The substance, whatever may be its nature, having been 
brought to perfect dryness, is covered with concentrated 
hydrochloric acid, the purity of which has been previously 
tested by operating on an equal quantity, according to a 
method to be presently explained (p. 540). The quantity of 
pure hydrochloric acid used must depend on the quantity of 
material for analysis. It should be sufficient to break up, 
dissolve, or mix freely with the whole of the solid. The 
mixture should be made in a retort or flask fitted with a 
condensing tube, and then gradually heated by a sand-bath, 
until the acid liquid begins to pass over. The retort or flask 
may be connected with a receiver closely fitting to it, and 
holding a small quantify of distilled water. The water in 
the receiver should be just sufficient to condense and fix the 
acid vapours. The receiver, as well as condensing-tube, 
should be kept cool by wetting its surface with cold water or 
otherwise. The perfect condensation of the distilled liquid 
is ensured by this arrangement.* 
The distillation may be carried to dryness on a sand-bath, 
or nearly so; and it may be sometimes advisable, in order to 
ensure the distillation of the whole of the arsenic as chloride, 
to add to the residue in the retort another portion of pure 
and concentrated hydrochloric acid, and again distil to dry¬ 
ness. I have, however, found that portions of dried liver 
and stomach give up every trace of arsenic by one distilla¬ 
tion, when a sufficient quantity of hydrochloric acid has 
* As a substitute for a retort when the quantity of matter for distillation 
is not large, I have found a most convenient form of apparatus, to be a 
globular flask of thin glass, with a short neck. Into this is fitted a tube of 
hard glass, from two to three feet in length, and one quarter of an inch in 
the bore. It should just pass through the cork in the neck of the flask, and 
this end of the tube should be bevelled off obliquely to a point, in order to 
prevent any of the liquid in the flask from being carried over. The tube 
should be covered spirally with layers of blottiug-paper (kept constantly 
wetted), for at least two feet of its length, and should terminate in a 
Florence flask, to which it is fitted by a cork. This flask should be kept 
cool by immersion in a basin of water, or by covering its surface with wet 
