1825.] M, Berzelius on Silicium. 119 



instant of contact is oxidated at its expense, and deflagrates in 

 the midst of the nitre. The cause why silicium in lower temper- 

 atures is more easily oxidized at the expense of the carbonate 

 than of the nitrate of potash undoubtedly exists in the circum- 

 stance, that the affinity of potash for silica is necessary to dispose 

 it to combustion, and in the case of nitre, this co-operation is 

 not obtained, except in the elevated temperature in which the 

 acid of the salt undergoes decomposition. 



Silicium deflagrates with brilhant ignition in the hydrates of 

 the fixed alkalies ; and the deflagration takes place as soon as 

 the hydrate begins to fuse, and far below a red heat. It defla- 

 grates also, but with less intensity, in the hydrates of barytes 

 and lime. With the acid fluate of potash, it deflagrates in the 

 low temperature necessary to produce the fusion of the salt ; in 

 melted borax it remains unaltered. 



If silicium be heated in the vapour of sulphur, it catches fire 

 and burns, but with much less brilliancy than in oxygen gas. 

 The product is a white earthy looking substance, which, in con- 

 tact with water, instantly dissolves, giving ofl* at the same time 

 sulphuretted hydrogen gas. The sihcium is here converted into 

 siHca, which is taken up by the water ; and if the quantity of that 

 liquid be small, the resulting solution is so concentrated, that it 

 gelatinizes after a very slight evaporation. In the open air this 

 sulphuret gives off" a strong odour of sulphuretted hydrogen gas, 

 and rapidly loses the whole of its sulphur: in an artificially 

 dried atmosphere, it may be preserved unaltered. When torre- 

 fied, it is converted, but not so rapidly as might have been anti- 

 cipated, into sulphurous acid and sihca. 



It is certainly a most remarkable property that silica, at the 

 instant of its formation in the humid way, should be so abun- 

 dantly soluble in water, and that by evaporation of the solution 

 it should lose this property so completely, that in the analysis 

 of minerals, it is justly regarded as insoluble. This high degree 

 of solubility enables us to understand the copious crystallization 

 of silica in drusy cavities, where, not unfrequently, the volume 

 of water could not possibly have greatly exceeded that of the 

 crystals which it deposited. 



I did not succeed in forming a phosphuret, by passing the 

 vapour of phosphorus over ignited silicium. 



When sihcium is heated in a current of chlorine, it catches 

 fire, and is rapidly volatilized. The product of the combustion 

 condenses into a liquid, which appears to be naturally colourless, 

 but which has a yellowish colour when it contains an exceiss of 

 chlorine. This fluid is very limpid and volatile, and evaporates 

 almost instantaneously in the form of a white vapour when 

 exposed to the open air. It has a suffocating odour, not unlike- 

 that of cyanogen. It re- acts as an acid on litmus paper. This 

 fluid is analogous to the combinations of the other electronega- 



