% 
290 Means of detecting Arsenic in the Animal Body, &e. 
matter submitted to analysis, destroying all remains of organic 
matter. Care must be taken that the nitre be in sufficient quan- 
tity, for if not, this part of the process must be gone over a second 
time. : 
After the deflagration has taken place, it may be well to heat 
the residtie a second time, in a capsule of platinum or silver, to 
redness. The residue consists generally of the following sub- 
stances: the excess of nitrate of potash mixed with the nitrite of 
the same substance; carbonate of potash ; the salts existing in 
the organic matter, as well as those formed during the process, 
such as the phosphates, sulphates and chlorides, free oxides, and 
finally arsenic acid, free and in combination with potash. This 
compound mass being pulverized, is mixed with one and a half 
times its bulk of hydrochlorate of ammonia, introduced into a 
retort, and heated toa dull redness. By the action of the heat, 
the chlorine of the hydrochlorate of ammonia combines with the 
potassium, and the hydrogen of the ammonia reduces the arsenic 
acid to the state of arsenious acid, which sublimes with the ex- 
cess of hydrochlorate of ammonia, and is condensed on the upper 
part and neck of the retort. Other chemical changes take place, 
but they do not modify the one just stated. ‘The operation being 
finished, the retort is broken, and the substance sublimed dissolved 
in water strongly acidulated with hydrochloric acid, and through 
this solution is passed sulphuretted hydrogen, which enables us 
to obtain all the arsenic that. was originally in combination with 
animal matter, in the state of a pure sulphuret. This process 1 
somewhat complicated, but each step is so clear, that with prope? 
care, the most satisfactory result might be obtained in almost all 
anes. Z 
In fulfilling the promise as regards the stating of all important 
facts lately brought to light concerning this too universal poison, 
I will mention two other methods of separating and of ascertail- 
ing the quantity of arsenic in combination with organic substan 
ees. They are both modifications of Marsh’s apparatus ; one 18 
proposed by M. Lassaigne, and the other by myself. 
. Lassaigne, instead of igniting the arsenuretted hydroge”, 
and obtaining the arsenic upon a cold surface, passes jt through 
solution of nitrate of silver, which it has the property of deco ae 
posing. The solution first becomes brown, and then a deposit © 
oxide of silver takes place. After the gas has ceased to pass, 4 
‘. 
