190 SULPHURETS. 



7. Sulphuret of magnesium is not so easily ob- 

 tained as the sulphurets of the preceding metals. 

 When sulphate of magnesia is heated in charcoal 

 almost the whole acid is dissipated, and nothing 

 remains but magnesia mixed with a small quan- 

 tity of sulphuret of magnesium. But sulphuret 

 of magnesium may be obtained in combination 

 with sulphuret of potassium, by heating a mixture 

 of sulphates of potash and magnesia in charcoal : 

 Berthier has shown that it is a protosulphuret of 

 magnesium which is thus obtained. It is a com- 

 pound of 



4 



1 atom magnesium . . 1-5 

 1 atom sulphur . . 2 



There was an excess of sulphur in the sulphuret 

 formed by Berthier, amounting to rather less than 

 1th of an atom. 



8. No attempts have been hitherto made to 

 form the sulphurets of aluminum, giucinum, 

 yttrium, or zirconium. It is by no means unlike- 

 ly that some of the processes tried by Berzelius 

 would succeed in forming these sulphurets also. 

 Iron ' 9. Sulphuret of iron. Iron and sulphur com- 



bine in three proportions. 



(1.) The protosulphuret may be formed by 

 heating a mixture of iron filings and sulphur in a 

 close crucible, and continuing the heat till the ex- 



