18Q7.1 145 [Fleury. 



of sulphide of silieium. It is also known tliat silica is always found 

 in sulphur springs. The simultaneous presence of these two products 

 in these waters, (which products are the results of the decomposition 

 of sulphide of silieium under the influence of Avater), together with 

 the chemical analogy that exists between the silica that comes from 

 the sulphide of silieium and that found deposited from the Geyser 

 snrings, (which ai-e equally as soluble in potassa), permit the supposi- 

 tion that the sulphide of silieium is not so rare as we may think at 

 present, and that it is probably produced in all cases where silica is 

 Ibund to be submitted to the action of a binary compound that yields 

 to it its sulphur and takes its oxygen, and that silicious waters can be 

 produced by the decomposition of sulphide of silieium in the presence 

 of water. AVhcn sulphide of silieium is heated in a current of humid 

 air, it is decomposed and forms silky cfystals of anhydrous silica. In 

 nature we meet certain varieties of silk-like quartz, the formation of 

 which may be due to the same cause. 



Here we have a flood of light on the history of our quartz and the 

 inclosed sulphurets; for, it can easily be deduced from the above 

 stated investigations, that as sulphuretted hydrogen can be dissolved 

 in water, it would be decomposed on coming in contact with a dissolved 

 oxide or hydrate of iron, and take the oxygen from the iron, which 

 latter would, in this case, combine with the sulphur of the decom- 

 posed sul{)liuretted hydrogen, and harden to a crystalline sulphuret 

 in the midst of the gradually hardening gelatinous silica. Berzelius 

 at first obtained the sulphide of silieium by passing the vapor of 

 sulphur over heated silieium. This compound is also produced in 

 small quantity by the action of sulphuretted hydrogen on chloride of 

 silieium. 



Pi'of. Fremy prepares his sulphide of silieium by submitting free 

 or combined silica to the action of bisulphide of carbon ; this de- 

 composition is much facilitated by mixing the silica with carbon, 

 coal-dust, etc. The silica prepared by chemical process so as to 

 be soluble in potassa, is much easier attacked by bisulphide of carbon 

 than ([uartz ; the same can be said of free silica ; however, certain 

 natural .silicates, feldspatlis for example, produce easily sulphide of 

 silieium when heated to a red heat and submitted to the action of 

 sul])hide of carbon. 



The composition of sulphide of silieium is easily found in decom- 

 posing by water a known weight of that body. Sulphuretted hydro- 

 gen is thereby disengaged, which is treated by the known method ; 

 the liquid is afterward evaporated and the residuary silica weighed. 

 Crystals of quartz, as well as of sulphurets of nearly all metals, have 

 been artificially produced by slow electric action, containing these 

 substances in solution. 



PROCEEPINGS B. 8. S. H.— VOL. XI. 10 jnLY, 1867. 



