292 
ON THE DETECTION OF ARSENIC. 
In the October number of the "Journal de Pharmacie," for 
the year 1840, is a paper by M. L. Figuier, upon the detec- 
tion of arsenic, in which the inconveniences of the Marsh 
apparatus are pointed out, and an important improvement 
recommended which removes all doubt as to the result. 
These inconveniences (alluding to the modified apparatus 
of Marsh, and more commonly employed — a simple bottle — 
mounted with atube,) are summedupunder the following heads. 
1st. The mixture of hydrogen and atmospheric air in the 
vessel forms detonating gas. In executing a toxicological ex- 
perimentyou incur thedangerofan explosion if you lightthegas 
too quick, with consequent breakage of the vessel and a loss of 
liquid probably irreparable; or to obviate ^this, you allow the 
gas as it disengages to escape for some time in order that the 
common air may be driven out, by which means you lose a 
certain quantity of arsenic, which, however small it may be, 
should not be viewed with indifference, when we consider 
the very small quantity generally contained in these experi- 
mental liquids. 
2d. A more seriousinconvenience,noteasily overcome, consists 
in the frothy development which, when it occurs, renders fur- 
ther operation very difficult. 
3d. The manner of inflaming the arseniuretted hydrogen as 
itescapesfrom the tube, and receiving the reduced metal upon a 
cold body, is liable to this disavantage. The flame of hydrogen 
gas applied to spots of metallic arsenic already formed, volati- 
lizes the metal, when the volume of flame is large and the ori- 
fice of the tube irregular. On the other hand it has been ob- 
served by experiment that a solution containing but a minute 
portion of arsenious acid does not show any stains upon por- 
celain, if the flame has but a very feeble intensity. 
For the above given reasons, Mr. Figuier considers Marsh's 
apparatus susceptible of improvement. 
Messrs. Liebig and Berzelius, acting under this belief, pro- 
posed to reduce the arsenic by applying heat to a part of the 
tube. Mr. Chevallier, adopting this modification, recommend- 
