Sulphur and Phosphorus with Platina. -31 



Collecting the results of these last experiments from the 

 retorts, there must have been a slight loss, which is not 

 noticed in the statements. Without regarding ihe frac- 

 tional paits, I venture to slate the composistion of 100 

 parts of super-sulphuret of platina as 



Platina 72 



Sulphur 28 



100 



4. Of Sul-Sulphuret of Platina. 

 This substance was procured by heating platina in con- 

 tact with sulphur in an exhausted tube. The tube em- 

 ployed was about four inches long, and Ij inch in dia- 

 meter; ai the open end it was made small for the con- 

 venience of being tasdy drawn off after exhaustion. The 

 materials were mixed and uitroduccd nearly in equal weights, 

 a stop-cock was then cemented to the tube, it was exhaust- 

 ed, hermetically sealed, and heated for about ten minutes 

 in an open fire; towards the end of the process, the bottom 

 of the tube was heated nearly to redness, to expel the ex- 

 cess of sulphur; the sub-sulphuret of platina alone re- 

 mained at tlie bottom of the tube. 



Physical and Chemical Properties. 

 Sub-sulphuret of platina is of a dull blueish-gray colour. 

 It is obtained in the form of powder, or in small pieces 

 the particles of which are loosely coherent. Its lustre is 

 earthy ; but when rubbed oh the fingers, or on paper, it 

 leaves a shinino maik of a blueish giay colour, having the 

 metallic lustre. It is rather harsh to the feel. It has no 

 smell or taste. Its specific gravity is about 6-2, that of di- 

 stilled water being 1. It is a nonconductor of electricity. 

 Like the super- sulphurct of platina, it does not appear to 

 be affected by exposure to the atmosphere, or in water. 

 Its chemical [)roperlies closely resemble those of the super- 

 sulphuret. The mineral acids scarcely aflect it at a boiling 

 heat. It is decomposed when heated w^ith oxymuriale of 

 potash or zinc filings. 



Analysis. 



The only simple and accurate method of deternnining the 

 composition of sub-sulpliurel of platina appeared to me to 

 be by the agency of heat, and to this mode 1 had recourse. 

 In tlie direct union of its elements, there was always a loss 

 arising from the circumstance that sulphur remains' fluid at 



high 



