278 EXAMINATION FOB PHOSPHORUS. 



placed, which combines with all the remaining arsenic, 

 forming steel-gray arsenide of copper. The increase 

 of weight of the tube indicates the amount of arsenic, 

 which is calculated as arsenious acid. 



129. EXAMINATION FOR PHOSPHORUS IN CASES 

 OF POISONING. 



Since phosphorus has been used to poison mice, &c., 

 and the poisonous action of friction matches has become 

 extensively known, phosphorus has not ^infrequently 

 been resorted to as an agent for causing death. It is 

 often necessary, therefore, to examine some article of 

 food, or the contents of a stomach, for this substance. 

 It is obvious that, in cases of the kind, his whole 

 attention must be directed to the separation of the 

 phosphorus in ihefree state, or to producing such reac- 

 tions as will enable him to infer the presence of free 

 phosphorus ; since the mere finding of phosphorus in 

 form of phosphates would prove nothing, as phosphates 

 invariably form constituents of animal and vegetable 

 bodies. 



A. Detection of Unoxidized Phosphorus. 



I. Test in the first place the suspected matters as to 

 whether free phosphorus is recognizable by its odor or 

 by its luminosity in the dark, exposing, for this pur- 

 pose, the materials to the air, as much as is necessary, 

 by rubbing, stirring, or shaking. 



II. A portion of the substance is placed, according 

 to the plan of J. Scherer, in a small flask; suspend in 

 it, above the substance, by aid of the loosely fitted cork, 

 a slip of filter paper moistened with neutral solution 

 of nitrate of silver, and warm the whole to 85 to 105 



