ON THE DETECTION OF ARSENIC. 
293 
ed a further improvement by the introduction into the tube of 
disengagement, of fragments of porcelain, with the double ob- 
ject of multiplying the heated surfaces offered to the passage 
of the gas, and to effect the separation of antimony from the 
arsenic, sometimes accidentally mixed with it. By decom- 
posing a mixture of arseniuretted hydrogen and antimony, 
the arsenic condenses in the cool part of the tube, and the an- 
timony deposits upon the heated pieces of porcelain. This 
mixture, however, rarely occurs. 
Mr. Figuier not being able to find in any of the methods 
yet proposed one which he could adopt with perfect confi- 
dence, for the detection of arsenic in organic matter, ventures 
to supply the deficiency by giving a process which, he says, 
reunites all the conditions necessary to complete success. 
He, however, enjoins upon the experimenter the precaution to 
have perfectly pure re-actives, (free from arsenic.) 
Description of Figuier' s process. 
The suspected matters, as usual, are cut up in pieces. 
Introduce them into a glass matrass and cover them over 
with a convenient quantity of water. The matrass is placed 
upon a sand bath, the water carried to ebullition and sustained 
for four or five hours,keeping up a very feeble alkaline reaction. 
When the decoction is cold, the fat swims, congeals and sepa- 
rates: then filter: a reddish viscous liquid is collected, which 
passes slowly through paper. 
Evaporate the filtered liquid to dryness, first acidulating it 
slightly with hydrochloric acid, and let the residue be dried 
without carbonizing the substance. Then redissolve the 
animal extract in hot water and filter it. The brown liquid 
which passes is then submitted to a current of washed chlo- 
rine, until it ceases to be turbid under the influence of the cur- 
rent of gas, an operation which requires some time. The 
pale yellow precipitate which is abundantly produced, being 
separated by filtration, a tolerably fluid yellow liquor is ob- 
tained, which contains but a very small quantity of organic 
matter, rendering further operation easy from the absence of 
the frothy development. As the liquid contains some chlo- 
