154 Intelligence and Miscellaneous Articles. 



by means of the carbon which it contains, and would at the same 

 time form sulphurets : this supposition I found confirmed by experi- 

 ment. In fact, I have obtained the sulphurets of boron, silicon, 

 magnesium and aluminium, by submitting boracic acid, silica, mag- 

 nesia and alumina, to the action of sulphuret of carbon at a high 

 temperature. To facilitate the reaction, and remove the sulphuret 

 from the decomposing action of the alkalies contained in the por- 

 celain 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. 



I have ascertained by analysis that these sulphurets correspond to 

 the oxides from which they have been derived. 



I will now say a few words of the sulj^hurets obtained by the above 

 method. The sulphuret of silicon had been obtained in small quan- 

 tity by Berzelius in the reaction of sulphur upon silicon, and by 

 M. Pien'e in the decomposition of chloride of silicon by hydrosul- 

 phuric acid. I have obtained this substance with the greatest ease, 

 by passing the vapour of sulphuret of carbon over pellets of charcoal 

 and gelatinous silica placed in a porcelain tube heated to 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 vapour. 



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 lieated in a current of moist air, it is decom- 

 posed, and furnishes silky crystals of anhydrous silica ; it is evident 

 that we may explain by means of this experiment the natural pro- 

 duction 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 connect this curious property with those natural 

 conditions under which certain mineral waters and siliceous incrus- 

 tations are formed. 



As the sulphuret of siHcon is probably produced in all those cases 

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

 which cedes sul])hur to it, and at the same time appropriates its 

 oxvgen, 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 exist- 

 ence of silica and sulphureted hydrogen in the principal sulphurous 

 waters. This hypothesis is in some measure confirmed by the inter- 

 esting observations of M. Descloizeaux, which show that the sili- 

 ceous springs of the Geysers of Iceland contain a large quantity of 

 sulphureted hydrogen. 



I content myself with submitting these considerations to geolo- 

 gists, merely observing that, in explaining the formation of sulphu- 

 rous 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 aluminium were prepared like the sul- 

 phuret of silicon, and are likewise decomposed by water. 



