MEDICO-LEGAL CONTRIBUTIONS ON ARSENIC. 
445 
shape of a p;utter, and-pushed into the reduction tube to its 
centre. By turning the card the mixture is deposited 
without soiling other parts of the tube. The card is then 
withdrawn and the tube connected with the apparatus^ sup¬ 
porting its free end if necessary. The tube ought to be of 
Bohemian glass, and about one fourth of an inch external 
diameter. Chlorhydric acid is now added to the flask con¬ 
taining the marble; the carbonic acid evolved is dried in the 
other flask. The reduction tube must now be gently heated 
throughout its whole length until all moisture is expelled, 
both from its walls and from the mixture. When this is 
accomplished, and when (the air having been completely 
driven out) the bubbles of carbonic acid gas pass through at 
the rate of one a second, a lighted lamp may be placed in 
front of the mixture, and the mixture heated by another lamp 
flame. The greater part of the arsenic will condense near 
the drawn-out end of the tube ; a small portion will escape 
from the tube, producing a garlic odour in the atmosphere. 
By carefully heating the tube before and behind the deposit 
it may be collected in a small spot, and will have a highly 
lustrous metallic appearance. If it is to be preserved, the 
point may be sealed by the blow-pipe flame, the other ex¬ 
tremity drawn out and sealed in a similar manner. The 
deposit may, of course, be converted into arsenious acid by 
oxidation, dissolved in water, and the liquid tests applied. 
The advantages of Fresenius^ and Babo’s test are these : 
1. It is simple and easy of execution. 
2. It is impossible to confound arsenic with antimony. 
Antimony compounds do not furnish any deposit under these 
circumstances. 
3. It is a delicate test; the -r^th part of a grain may be 
detected by careful manipulation. It is not, however, nearly 
so delicate nor so readily applied as Marshes test. 
[To he continved.) 
