30 On the Combinations of 



heat in vessels excluded from the air; but in the atmosphere 

 it undergoes partial decomposition at a moderate heat, the 

 sulphur burns with a blue flame, and sulphureous acid gas 

 is formed : at a dull red it is completely decomposed, and 

 the plalina remains in a state of purity. 



Analysis. 



The mineral acids could not be employed to ascertain 

 the composition of super-sulphuret of platina. It might 

 be analysed by the agency of zinc filings and the acids ; but 

 it was unnecessary 'o resort to complicated processes, when 

 methods more simple, and susceptible of greater accuracy, 

 could be adopted. As it was readily decomposed by heat, 

 and the quantity of metal in a given weight of the am- 

 monia-muriate of platina easily ascertained, its composi- 

 tion could be determined both by analysis and synthesis. 



From two experiments made in both of these methods 

 with considerable precaution, its component parts are de- 

 duced. 



First Experiment . 10 grains of super-sulphuret of platina 

 decomposed by heat in a platina crucible afforded 7*17 

 grains of pure platina. 



Second Experiment. 8 grains of super-sulphuret decom- 

 posed by heat on a piece of Florence flask, furnished 5'75 

 grains of platina. 



From the first of these experiments 100 grains of super- 

 sulphuret of platina contain 



Platina 71-7 



Sulphur .... 2S'3 



1000 



For 10 : 7-17 : : 100 : 71-7. 



From the second, 100 grains contain 



Platina 71 '87 



Sulphur.... 28*13 



100-00 



For 8 : 5-75 : : 100 : 71-87. . 



In the two synthetical experiments 10 grains of the am- 

 monia-muriate of platina, heated with sulphur, furnished 

 in one case 6-14 grains, and in the other 61 grains of 

 super-sulphuret. 



Now 10 grains of the ammonia-muriate of platina con- 

 tained 445 grains of platina. Hence these experiments 

 indicate rather less sulphur than the preceding ones; but 

 the difference is trifling, aud is easily accounted for. In 



collecting 



