120 M. Berzelitts on Silicium. [Aug. 



tive substances with chlorine. It constitutes the second known 

 example of a volatile compound of sihcium. No combination 

 ensued when silicium was heated in the vapour of iodine. 



Silicium is neither dissolved nor oxidized by the sulphuric, 

 nitric, or muriatic acids, nor even by aqua regia. While still 

 combustible, it is slowly dissolved by fluoric acid, but even in 

 this acid, it loses its solubility after having been ignited. On 

 the contrary, it is readily dissolved in the cold by a mixture of 

 the fluoric and nitric acids. 



Silicium, after it has been insulated, possesses very little ten- 

 dency to form alloys with metals. Copper, silver, lead, and tin, 

 may be fused with it before the blowpipe, and the alloys, when 

 dissolved in acids, leave behind an inconsiderable portion of 

 silica. The alloy of copper leaves a skeleton of silica which 

 retains the original form of the metal.''^ 



Composition of Silica. — Having* now succeeded in isolating 

 the basis of silica, it was natural for me to investigate its composi- 

 tion by the direct synthetical process. With tliis view, 100 

 parts of pure silicium were ignited with carbonate of soda: the 

 mass was treated with muriatic acid, evaporated to dryness, and 

 the residue strongly ignited. Digested in water, this left a grey 

 coloured silica, which, after washing and ignition, assumed a 

 snow white colour, and weighed 203*75 parts. The liquid 

 filtered from the silica was again evaporated to dryness, and the 

 saUne mass ignited. By dissolving the fused salt in water, there 

 separated an additional quantity of silica, weighing, after igni- 

 tion, I'o part. Consequently 100 parts of silicium had combined 

 with 105-25 parts of oxygen* On repeating the experiment 

 with a portion of silicium over which I had previously evaporated 

 to dryness some fluoric acid, the augmientation of weight 

 amounted to 108 per cent. According to these two experiments, 

 silica is composed of 



Silicium 48-72 48-08 



Oxygen 51-28 51-92 



Both results indicate a larger proportion of oxygen than has 

 been hitherto supposed to exist in silica. According to my 

 Earlier experiments, in which I deduced the composition of 

 silica by determining its capacity of saturating saline bases, the 

 (Quantity of oxygen was only 50-3 per cent. 



The saturating capacity of silicium may be calculated also 

 from the composition of the salts which contain fluate of silica. 

 Of these, the most suitable for this purpose is the silicated 

 fluate of barytes. 100 parts of this salt, fused with twice its 

 Weight of oxide of lead, lost 0-85 part of moisture. 100 parts. 

 Weighed out at the same time, yielded 82-933 parts of sulphate 



* The methotl of preparing silicium, by deconiposiug the double fluate of silica and 

 «6da, has been alteady described in the Annals, N, S. vol. viii. p. 122. 



