258 EXAMINATION FOR ARSENIC 



evaporated, and the residual mass ignited, with access 

 of air, until only pure sesquioxide of iron is left. 



Ferrocyanide of potassium may probably also be 

 decomposed by beating with bisulphate of ammonia. 

 The residue after ignition would then consist of a 

 mixture of sesquioxide of iron and sulphate of potassa, 

 from which the latter might be extracted with water. 

 Or, to insure an accurate result, the ignited residue 

 might be dissolved in hydrochloric acid, the sesqui- 

 oxide of iron precipitated by ammonia, the solution 

 evaporated, and the residual sulphate of potassa ig- 

 nited and weighed. 



128. EXAMINATION FOR ARSENIC IN CASES OF 

 POISONING. 



When poisoning by arsenic is suspected, the poison 

 must be sought in the contents of the stomach and in- 

 testines, in the substance of these organs even, and in 

 other entire organs, as the liver, spleen, and lungs; an 

 examination must also be made of the vomited matters, 

 and of the surrounding objects, upon which these may 

 have fallen ; the urine and faeces should also be tested 

 for arsenic. The nature of the case will decide in 

 which particular direction the arsenic is to be looked 

 for. It may also sometimes be necessary to examine 

 the remaining portions of suspected food, or the ves- 

 sels, in which the food has been contained, or even the 

 vessel or paper which may have been used to contain 

 the arsenic. When the body has been long interred, 

 and is far advanced in putrefaction, and the wood of 

 the coffin has rotted away, it becomes necessary to test 

 the surrounding earth for arsenic which may have 

 been derived from the body. 



The chemical investigation must be preceded by a 



