pear. The matter enters first into solution, and then becomes 
carbonized during the concentration of the liquid, which we con- 
tinue to evaporate, stirring at the same time with a glass rod. 
The carbonization takes place without any swelling up of the 
materials, (as is the case when nitric acid is used.) The action 
of the heat is prolonged until the carbon appears friable and al- 
most dry. The capsule is now left to cool, and then there is 
added to the carbon about the same quantity of nitric acid as we 
did of sulphuric acid in the first part of the operation. This 
serves to convert the arsenious into arsenic acid, which latter is 
much more soluble than the former: we again evaporate to dry- 
ness, and treat the residue with boiling water, which dissolves 
the arsenic acid only, and is always perfectly limpid, and some- 
times colorless ; and this liquid also, when introduced into Marsh’s 
re sou produces no froth.” 
“This 
process is much preferable to the carbonization by nitric 
much - 
atid; for we can more easily manage the operation, and a 
less quantity of reactives is required, (an neonsacrene ey 
and there never is any deflagration.” 
MM. Danger and Flandin recommend the use of idea onal 
er quantity of nitric acid than has been stated, but from the pro- 
duction very often of phosphite and sulphite of ammonia during 
the action of the sulphuric acid upon the animal matter, it is ve- 
ry necessary that there should be sufficient nitric acid to convert 
these compounds into phosphate and sulphate of ammonia, for 
otherwise our experiments would be singularly confused, as will 
be shown a little farther on. It would appear that the arsenious 
acid in the operation just stated, would be evaporated along with 
. the sulphuric acid, but some experiments performed by the com- 
mittee before mentioned, with reference to that spe sountas pic 
no danger need be apprehended on that score. 
I have now stated: the best method to pursue, in ashuae 
liquid that may contain all the arsenic in combination with any 
organic matter, and also one that is proper to be introduced into 
Marsh’s apparatus. The next question that most naturally arises 
is, what form of this apparatus is the one that is most calculated 
" give us einen results? - he committee of the Academy of 
ences lso occupied themselves with this question, and 
the following isa detailed account of the instrument sth. hee 
received their a 
Ete 
- ee 
