276 7? '(.'searches on Sulphurets Decomposable by Water. 



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 porcelain 

 tubes, it is sometimes useful to mix the oxides to be re- 

 duced with charcoal, and to form them into little balls similar 

 to those which are used in the preparation of the chloride of 

 silicon. 



T have ascertained by analysis that these sulphurets cor- 

 respond to the oxides from which they have been derived. 



I will now say a few words on the sulphurets obtained by 

 the above method. The sulphuret of silicon had been ob- 

 tained in small quantity by Berzelius in the reaction of sul- 

 phur 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 vapour 

 of sulphuret of carbon over pellets of charcoal and gelatinous 

 silica, placed in a porcelain tube heated to bright red. The sul- 

 phuret 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 shew the interest which attaches to the examination of 

 this substance, it will suffice to mention here two of its re- 

 actions. When sulphuret of silicon is heated in a current of 

 moist air, it is decomposed, and furnishes silky crystals of an- 

 hydrous silica ; it is evident that we may explain, by means 

 of this experiment, the natural production of certain filamen- 

 tous crystals of silica. The sulphuret of silicon in the pre- 

 sence of water is decomposed with a brisk evolution of hydro- 

 sulphuric 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 incrustations are formed. )il 



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, 



