ON THE DETECTION OF ARSENIC. 
289 
ticity, from the liquid in which it is produced, and may be 
collected in an ordinary gas recipient for future examination. 
It presents the means of obtaining in a direct manner, small 
quantities of arsenic from viscous alimentary liquids, such as 
gruel, soup, porter, coffee, wine, &c. 
This apparatus, as represented in fig. 4, consists of a glass 
tube open at both ends, and about fths of an inch in its inter- 
nal diameter. It is bent in the form of a syphon , the shorter leg 
being about five, and the longer eight inches in length. A stop- 
cock, ending in a jet of fine bore, passes tightly through a hole 
made in a sound cork, which fits air tight in the opening of 
the shorter branch. Lastly, the apparatus is placed in an up- 
right position, and braced to a wooden support. 
A bit of glass rod, A, about an inch long, is dropped into the 
shorter leg, followed by a piece of pure sheet zinc, B, bent 
double, or coiled so that it runs down the tube till it is stop 
ped by the piece of glass rod first put in. 
When you wish to experiment upon a suspected liquid, mix 
it with a certain quantity of distilled sulphuric acid, (one part 
acid to seven of liquid,) and pour it into the long branch of 
the apparatus, until it stands in the short one about ith of an 
inch below the cock kept open. Bubbles of gas will be seen 
to rise from the zinc, which are pure hydrogen if no arsenic 
be present, but if the liquid holds arsenic in any form in solu- 
tion, the gas will be arseniuretted hydrogen. Allow the first 
portions to escape, in order to drive out the atmospheric air, 
then close the cock, and the gas will collect in the shorter 
leg and drive the fluid up the longer one till the liquid has 
descended in the short leg below the piece of zinc, when no 
more gas is produced, as in the case of the hydrogen gas 
lamps. 
Upon quickly igniting the gas as it issues from the jet, and 
then holding horizontally in contact with the flame a plate of 
glass or porcelain saucer, the arsenic will be found deposited 
upon these cold bodies in the form of round spots of a grayish 
black color and metallic lustre. If no arsenic be present, then 
vol. iv. — no. iv. 37 
