DETECTION OF UNOXIDIZED PHOSPHORUS. 281 



of turpentine, no luminosity is observed so long as 

 these substances continue to distil over. In the case 

 of ether and alcohol, however, this is soon effected, 

 and the luminosity accordingly very speedily makes 

 its appearance ; but it is different with oil of turpentine 

 which exercises a lasting preventive influence upon 

 the manifestation of this reaction. 



a. After the termination of the process, globules of 

 phosphorus are found at the bottom of the receiver, 

 C. Mitscherlich obtained from 5 oz. of a mixture con- 

 taining ^ grain of phosphorus, so many globules of 

 that body that the one-tenth part of them would have 

 been amply sufficient to demonstrate its presence. In 

 medico-legal investigations these globules should first 

 be washed with alcohol and then weighed. A portion 

 may afterwards be subjected to a confirmatory exami- 

 nation, to make quite sure that they really consist of 

 phosphorus : the remainder, together with a portion of 

 the fluid which shows the luminosity upon distillation, 

 should be sent in with the report. 



The experiment should be made in a perfectly dark 

 room, best at night. If it is made in the daytime the 

 room should be darkened by aid of curtains or blinds, 

 so that no reflections whatever from the surfaces of the 

 glass vessels or of the fluids moving in them shall oc- 

 casion mistakes. It is advisable, even, especially when 

 very minute traces of phosphorus are searched for, to 

 pass the evolution-tube through a screen, at 5, to pre- 

 vent such reflections being occasioned by the light of 

 the lamp by which the flask is heated. 



The residue of the distillation is further examined 

 according to (VI.) for phosphorous acid. The distil- 

 late, also, may be tested in the same manner to confirm 

 the presence of phosphorus, or of phosphorous acid 

 arising from its oxidation. 



IV. Another sample of the substance may be exa- 

 mined, according to experiments made by Neubauer 



24* 



