260 M. Berzeliiis on the Prfj)aration 



sulphur, that the silicium becomes completely sulj)huretted, 

 at least in a pait of its mass. It then presents an earthy wliite 

 body, which, thrown into water, instantly dissolves in it with 

 the evolution of sulphuretted hydrogen. The silicium is con- 

 verted into silica which dissolves in the water; and if this is in 

 small quantity, a solution may be obtained so much concen- 

 trated, that it solidifies after a slight evaporation, and it 

 leaves the silica, after the desiccation, in a transparent fissured 

 mass. Silicium imperfectly sulphuretted also decomposes 

 water rapidly, with the disengagement of hydrogen, and solu-- 

 tion of the silica in the water ; and the silicium which was not 

 combined with the sulphur becomes separated. In the air 

 the sulphuret of silicium diffuses a very strong smell of sul- 

 phuretted hydrogen, and loses in a little time all its sulphur ; 

 but in dry air it may be preserved a long time. At a red heat, 

 it contracts and shrivels up, yielding sulphurous acid and silica. 

 This change, however, takes place but slowly ; for when kept 

 at a red heat for some moments, it still has the property of 

 decomposing water. 



The siliciuret of potassium readily combines with sulphur 

 at a red heat ; but if the mass is dissolved in water, there re- 

 mains much silicium, imless the mass be newly exposed to a 

 white heat, because the silicium then combines w^ith the sul- 

 phur at the expense of the potassium previously sulphuretted 

 at a more elevated temperature. This combination is a true 

 double sulphuret; its colour is of a dark brown, almost black. 

 It presents a melted mass which dissolves in water. It is dif- 

 ficult to say whether it dissolves without changing its nature; 

 but since the sulphuret of silicium is decomposed in water, 

 and sulphuretted hydrogen has a great affinity for the sul- 

 phuret of potassium, it is very probable that in the solution 

 there exists some silicate of potash with hydro-sulphuret of 

 the same alkali. The combinations of the sulphuret of sili- 

 cium with the metallic sulphurets, although they exist in the 

 dry way, cannot, it appears, exist in water. 



It is certainly a very remarkable fact to see the silica dis- 

 solve in so great quantity in water at the moment of its forma- 

 tion, and lose this property by evaporation, so as to become 

 insoluble in acids. This great solubility, shown by the pre- 

 ceding experiments, explains the numerous crystallizations of 

 silica in the cavities of druses, which sometimes could not con- 

 tain a volume of liquid ever so little greater than the crystal it- 

 self Nevertheless, I do not pretend that the silica had been 

 in solution as in our example ; that is to say, that it was the 

 result of the decomposition of the sulphuret of silicium. 



I did not succeed in combining phosphorus with silicium 



by 



