290 Means of detecting Ai^senic in the Animal Body, S^c. 



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 residue 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 to a 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 is 

 somewhat complicated, but each step is so clear, that with proper 

 care, the most satisfactory result might be obtained in almost all 

 cases. 



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 ascertain- 

 ing the quantity of arsenic in combination with organic substan- 

 ces. They are both modifications of Marsh's apparatus ; one is 

 proposed by M. Lassaigne, and the other by myself. 



M. Lassaigne, instead of igniting the arsenuretted hydrogen, 

 and obtaining the arsenic upon a cold surface, passes it through a 

 solution of nitrate of silver, which it has the property of decora- 

 posing. The solution first becomes brown, and then a deposit of 

 oxide of silver takes place. After the gas has ceased to pass, a 



