212 ANNUAL OF SCIENTIFIC DISCOVERY. 



confirmed by experiment. In fact, I have obtained the sulphurets of 

 boron, silicon, magnesium and aluminum, by submitting boracic acid, 

 silica, magnesia and alumina to the action of sulphuret of carbon at a 

 high temperature. To facilitate the reaction, and remove the sul- 

 phuret from the decomposing action of the alkalies contained in the 

 porcelain tubes, it is sometimes useful to mix the oxides to be reduced 

 with charcoal, and to form them into little balls similar to those which 

 are used in the preparation of chloride of silicon. These sulphurets 

 correspond to the oxides from which they are derived. 



The sulphuret of silicon had been obtained in small quantities by 

 Berzelius in the reaction of sulphur upon silicon, and by M. Pierre 

 in the decomposition of chloride of silicon by hydrosulphuric acid. 

 I have obtained this substance with the greatest ease, by passing the 

 vapor of sulphuret of carbon over pellets of charcoal and gelatinous 

 silica placed in a porcelain tube heated to a bright red. The sulphuret 

 of silicon condenses in the tube in beautiful white silky needles, which 

 are not very volatile, but are readily carried along by the vapor. To 

 show the interest which attaches to the examination of this substance, 

 it will suffice to mention here two of its reactions. When sulphuret 

 of silicon is heated in a current of moist air, it is decomposed and 

 furnishes silky crystals of anhydrous silica ; it is evident that we may 

 explain by means of this experiment the natural production of certain 

 filamentose crystals of silica. The sulphuret of silicon in the presence 

 of water is decomposed with a brisk evolution of hydrosulphuric acid 

 into silica, which remains entirely dissolved in the water, and is not 

 deposited until the liquid is evaporated. It is impossible not to con- 

 nect this curious property with those natural conditions under which 

 certain mineral waters and siliceous incrustations are formed. As the 

 sulphuret of silicon is probably produced in all those cases where 

 silica is submitted to the double action of a binary compound which 

 cedes sulphur to it, and at the same time appropriates its oxygen, this 

 sulphuret is probably not so rare as has been hitherto thought ; and 

 by admitting its presence in those rocks in which sulphurous springs 

 occur, we might explain the simultaneous existence of silica and 

 sulphuretted hydrogen in the principal sulphurous waters. This 

 hypothesis is in some measure confirmed by the interesting observa- 

 tions of M. Descloizeaux, which show that the siliceous springs of the 

 Geysers of Iceland contain a large quantity of sulphuretted hydrogen. 

 In explaining the formation of sulphurous and siliceous waters by the 

 decomposition of the sulphuret of silicon, I am only extending the 

 ingenious theory proposed by M. Dumas to explain the formation of 

 boracic acid. The sulphurets of boron and aluminum were prepared 

 like the sulphuret of silicon, and are likewise decomposed by water. 

 The sulphuret of magnesium I obtained by passing sulphuret of car- 

 bon over pure magnesia ; in this case the presence of charcoal does 

 not appear to be of any use. This sulphuret crystallizes and is soluble 

 in cold water ; when its solution is kept at the ordinary temperature, 

 there is but a feeble disengagement of sulphuretted hydrogen ; but 



