¢ 
158 On Tests for the Discovery of Arsenic. 
[ used in these experiments, achromat of potash made in 
the imperfect and impure way in which Dr. Porter used it; 
and also another solution made in the usual way. That 
is, I took two oz. avoird of triturated chromated iron, and 
added to it, one oz. avoirdupois of triturated nitre : to other 
two oz. avoirdupois of chromated iron, [ added one oz. of 
dried salt of tartar: I exposed them in separate crucibles to 
a full red heat for 1" hour (side by side) in a common forge = 
I washed the contents of each crucible in the same quantity 
of boiling water, and filtered. On testing them with super- 
acetat of lead, the yellow produced by the nitrated chroma- 
ted iron, was of a richer colour than the other ; which last 
contained not only uncombined alkali, but also a portion of 
oxyd of iron, which covered the precipitate of lead. But. 
in making the experiments detailed in this paper, I found 
no perceptible difference of result between the two solu- 
tions. In ae variance between Dr. Porter’s experiments 
and cad os desirable that other persons should repeat 
nr ; and wi ith b acta ae you remar 
The su ubject ought to be investigate ‘in every point of view, 
until Ol mists sare enabled t i ju- i 
“ryy fw ede: possess: sure and accurate means of. detecting 
the poison: of arsenic.” 
Of the methods hitherto proposed for this purpose, the fol- 
lowing appears to me the best ; deduced from the result of 
Pa own experiments, and of the chemists who have epee 
de 
Sapbots a man sispected: of being poisoned. by. arsenic : 
let the ejections from his stomach, (and the contents of his: 
stomach, if dead,) be examined. carefully with a magnifying 
glass, to ccueauee the particles of white arsenic.in substance, 
which should be set aside for experiment. If you find no 
such appearance, let the matter ejected, and contained, be : 
fully dried in a heat of not less than 100° Fah. Take some 
of the dried matter, triturate it with ;';th of its weight of dry 
lamp black, ivory black, orcharcoal ; into.a glass tube six or 
nine inches long, half an inch wide, and-closed atone end, put 
as much of this: mixture as will fill the tube from half an inch 
to an inch deep ; ; stop the open end lightly with a cork ; ex= 
pose the matter in the flame of an oil or spirit lat ; 
here be any arsenic, it will shortly sublime in black shining 
metallie particles toward the upper end of the tube. These 
