294 
ON THE DETECTION OF ARSENIC. 
rine which would decompose the nascent arseniuretted hydro- 
gen, it must be placed in a porcelain capsule and heated to ebul- 
lition to drive off the chlorine. The liquid is now fit to be 
introduced into the apparatus. 
The apparatus, which is a modification of that of Marsh, is 
similar to that represented in fig. 6th, and very much the 
same as is used in the laboratory of the School of Pharmacy 
of Montpellier, by Messrs. Balard and others engaged in toxi- 
cological analyses. 
It consists of as traight necked bottle, holding about |ths of a 
quart, and fitted with a cork traversed by two tubes. The one 
surmounted by a funnel reaches to the bottom of the liquid con- 
tained in the bottle, the other is a bent tube of about 7 or 8 
millimetres (3 lines) in diameter, and finely drawn out at its 
extremity. A convenient way of forming this tube is to 
make it of two others. One of common diameter connected 
with the cork and bent, the other of the diameter indicated, to 
contain the chloride of calcium and porcelain. They may be 
connected by sheet caoutchouc. 
Place in the horizontal tube, first, some pieces of fused 
chloride of calcium, and afterwards some fragments of porce- 
lain, and afterwards apply heat to this part of the tube. 
For this purpose, arrange a small grate, about four inches 
lengthwise and two in breadth, formed of three rectangular 
plates of sheet iron, of which the inferior one should, be pierced 
with holes to give passage to the air, and should also support 
the tube to be heated. Two bricks placed under this will give 
it the proper elevation. (See fig. 7.) 
As the tubes are unable to support a red heat without melt- 
ing, choose for the tube, glass as little fusible as possible, wrap 
around the part exposed to the fire a sheet of scraped copper, 
and fasten this with copper wire. 
The tube, thus protected, can neither be deformed or v ob- 
structed by fusion. 
Commence now, by pouring through the straight tube into 
the bottle, containing about twelve drachms of zinc, some sul- 
phuric acid, diluted with seven times its weight of water. The 
