Memis of detecting Arseiiic in the Animal Body, i^c. 289 



until the mass becomes perfectly dry ; water is now poured upon 

 it, and heat applied for ten or fifteen minutes ; the liquid is now 

 filtered, and tested by the apparatus. The heart, muscles, brain, 

 &c., if examined, must undergo the same process. 



There is yet another advantage, that has not been mentioned, 

 connected with the carbonization of animal matter by nitric acid; 

 it is, that if antimony be present, it becomes converted into anti- 

 monious acid, which is insoluble in water. 



Mention has been made only of the manner of separating 

 arsenic from animal matter, by the aid of Marsh's apparatus, 

 and it may be well to give a brief account of one or two new 

 methods adopted by Mr. Persoz to serve the same end, with this 

 additional advantage, that it enables one to ascertain the exact 

 amount present. 



The suspected materials, after having sufficient reason to sup- 

 pose that they do not contain a poison of organic origin, or mer- 

 curial or antimonial preparations, are subjected to the action of 

 dilute nitric acid, in order to destroy those parts that are decom- 

 posed by this agent. Most of the organic substances having un- 

 dergone this decomposition, the residue is diluted with water, and 

 heated to the boiling point, and then left to cool ; the fatty and 

 resinous substances rise to the surface, are taken off and washed, 

 and the washings added to the original liquid, which is then 

 evaporated to the consistency of syrup. The liquid now has a 

 dark brown tint, an evidence that it still contains a quantity of 

 organic matter. Nitric acid, therefore, is again added, and a new 

 oxidation takes place. We recommence to evaporate, and con- 

 tinue to add nitric acid, until the liquid acquires a lively orange 

 tint, when a careful evaporation is commencedj first over a naked 

 fire, and then by the means of vapor. An approximate value be- 

 ing made of the quantity of residue, twice and a half times its 

 volume of pure nitrate of potash is added, for the purpose of com- 

 pleting the oxidation. Water is next poured upon these materi- 

 als, and heat applied and continued until the water is evaporated 

 and the residue is dry ; by this means an intimate mixture is 

 brought about between the nitre and animal substances. In this 

 part of the operation, care must be taken to extend the matter as 

 much as possible over the surface of the capsule as soon as it be- 

 gins to dry. The capsule is now heated almost to redness, when 

 a deflagration takes place, and propagates itself through all the 



