308 
-SELECTED ARTICLES. 
guity of clarification and other processes whereby liquors, 
suspected of containing arsenic, are prepared for the exhibition 
of the usual tests, or of evaporation and deflagration which are 
sometimes had recourse to in order to separate the arsenic 
from the organic substances with which it may have been 
mixed. 
I had the satisfaction of finding, on trial, that my anticipa- 
tions were realized; and that I was thus able, not only to se- 
parate very minute quantities of arsenic from gruel, soup, 
porter, coffee, and other alimentary liquors, but that, by con- 
tinuing the process a sufficient length of time, I could elimi- 
nate the whole of the arsenic in the state of arsenuretted hy- 
drogen, either pure, or at most, only mixed with an excess of 
hydrogen. 
If this gas be set fire to as it issues from the end of a jet of 
fine bore into the common air, the hydrogen, as the more com- 
bustible ingredient, will burn first, and will produce aqueous 
vapour, while the arsenic will be deposited either in the me- 
tallic state, or in that of arsenious acid, according as it is ex- 
posed partially or freely to the air. The former condition is 
brought about by holding a piece of cold window glass oppo- 
site to and in contact with the flame, when a thin metallic 
film will be immediately deposited on its surface; and the 
latter, by receiving the flame within a glass tube open at both 
ends, which in half a minute, will be found to be dimmed by 
a white pulverulent sublimate of arsenious acid. By direct- 
ing the flame obliquely within side of the tube, it strikes 
against the glass and deposits the arsenic partly in the metal- 
lic state. In this case, if the tube, while still warm, be held 
to the nose, that peculiar odour, somewhat resembling garlic, 
which is one of the characteristic tests of arsenic, will be per- 
ceived. Arsenuretted hydrogen itself has precisely the same 
odour, but considerable caution should be used in smelling to 
it, as every cubic inch contains about a quarter of a grain of 
arsenic. 
The requisite apparatus is as simple as possible; being a 
glass tube open at both ends, and about three quarters of an 
