§ 77-6-] ARSENIC. 607 
expelled by boiling, and the final sulphuric acid tested for arsenic in the 
modified Marsh apparatus already described. 
The apparatus recommended by Gautier has been modified somewhat 
by Gabriel Bertrand, and as, in essential principles, it is the same as 
Gautier’s apparatus slightly improved, it will suffice to describe here 
only Bertrand’s process. 
The apparatus consists of a flask of 90 c.c. capacity, in which the 
reduction of the arsenical compound is effected by zinc and sulphuric 
acid. The flask is furnished with a long tube and cylindrical funnel, E, 
to which is fixed by means of a cork the bulb tube, A, furnished with a 
stop-cock. The gas passes through the tube, L, 30 c.c. long, charged 
with highly dried cotton-wool; to this tube succeeds C, made of diffi¬ 
cultly fusible glass—the internal diameter is 1 mm., and the walls 
2 mm. thick. The tube is surrounded by asbestos, and heated by a 
“ ramp ” of gas for the length of 10 c.c. ; 3 c.c. from the heated part a 
small stream of cold water, dropping on a piece of filter-paper wrapped 
around the tube, cools the issuing gas, which finally bubbles through 
water at V. 
The method of procedure with this apparatus is as follows :—10-20 
grms. of granulated zinc are introduced into a flask, with 30 c.c. of 
water and a few drops of a solution of platinum chloride. As soon as 
the zinc is platinised, which is denoted by the bright surfaces becoming 
of a dull grey-black, the water is poured away, and, after washing the 
zinc with a little distilled water, the zinc is transferred to the flask F, 
and the apparatus connected up. The air is now displaced by a current 
of dry carbonic acid gas, and 10 c.c. of sulphuric acid (1 of acid to 4 of 
water) added ; a brisk effervescence follows, and the carbonic acid gas 
is expelled from the apparatus by the hydrogen; 10 cm. of the 
capillary thick-walled tube is now brought to a dull-red heat, and the 
