150 
ON THE DETECTION OP ARSENIC. 
to use oxidising agents to destroy these, and to convert the 
arsenious into arsenic acid; but, besides these modes being 
very tedious, the new arsenical products generally present 
more difficulty in the endeavor to reduce the arsenic, than 
when we act on the arsenious acid itself. 
Therefore it is proper, under many circumstances, to treat 
the organic matters containing small quantities of arsenic, 
first, by ebullition in water, and reduce the liquid to a small 
bulk; and afterwards add alcohol; we would then obtain a li- 
quid which, no longer viscid, would promptly pass the filter, 
and in which reagents would readily reveal the presence of 
arsenic. The same alcoholic arsenical liquor may be intro- 
duced into Marsh's apparatus, without producing the frothy 
effervescence which always takes place when animal matter 
is present. In fact, we know, that to obviate this effect Marsh 
himself has proposed to pour upon the surface of the liquid 
some drops of alcohol or of oil. 
Journ. de Pharm. 
Nancy, November 13M, 1840. 
