Remarks upon At^senic. 79 



4th. We may collect the arsenate of silver thus formed, mix 

 it with a little black flux, introduce it in the bulb by the extrem- 

 ity a of the tube ab, (which extremity is to be subsequently 

 closed by being heated,) and then heat the bulb, the arsenate 

 will be decomposed, and the arsenic will make its appearance in 

 the form of a metallic ring in the capillary portion of the tube b. 



In experimenting with Marsh's apparatus, we should of course 

 be sure of the purity of the materials used in generating the hy- 

 drogen gas, as well as of those used for carbonizing the animal 

 matter. We should submit them all to the same examination 

 alone, as we did in company with the substance which was the 

 object of our experiment, that is to say, we should evaporate to 

 dryness the same quantity, or even more sulphuric and nitric acids 

 and water than was used, and test it with the same quantity of 

 zinc. It must be understood at the same time, that all the re- 

 agents should be tested before as well as after the experiment. 



In my last letter, I mentioned that it was generally supposed 

 after the experiments of M. Orfila and others, that the bones con- 

 tained arsenic, and it was also believed that the muscles did ; 

 there having been obtained taches resembling in some degree 

 those of arsenic, which, I gave then as my opinion, were no 

 doubt caused by the sulphur and phosphorus contained in the 

 muscles. 



MM. Danger and Flandin have been occupying themselves 

 particularly with the investigation of the question of the exist- 

 ence of arsenic normally, in the animal economy. In their ex- 

 periments they found that by taking a small portion of a muscle, 

 and carbonizing it imperfectly, they were able to obtain taches 

 resembling in all respects those of arsenic, but which in reality 

 were not, for they ascertained that they were produced by the 

 sulphite and phosphite of ammonia and an animal volatile oil, 

 formed during the imperfect carbonization ; and also by the aid 

 of about one grain and a half of each of these salts and eighteen 

 drops of spirits of turpentine, they formed these taches in con- 

 siderable quantity ; they have stated that they resemble in all 

 respects those of arsenic, but no one accords with them on that 

 point. The committee of the Academy of Sciences stated what 



