266 M. Berzelius on Silicium. 



combined with 21-886 of silica, or that 100 of acid took 14.3*76 

 of silica. The filiate of silica is consequently composed of 



Fluoric acid 4 1 -024 lOO'OO 



Silica 58-976 143-76 



But 100 parts of fluoric acid correspond to 74-7194 of oxy- 

 gen in each base that it saturates; consequently this quantity 

 of oxygen ought to be contained in the 143-76 of silex which 

 the acid saturates, and the composition of silica should be 



Silicium 48-025 100-00 



Oxygen 51-975 108-22 



This proportion comes very near to that obtained by sjTi- 

 thesis, but it is difficult to say on which side the greatest errors 

 of observation aie to be found. According to what precedes, 

 the weight of the atom of silicium, supposing that the silica 

 contains three atoms of oxygen, would be 277-2, and, accord- 

 ing to the best of the two synthetic experiments, 277-8. The 

 other would carry it to 285 ; but this number by all appear- 

 ance is too great. It exceeds by If per cent that which had 

 been adopted at first ; which is so well suited for the new and 

 most exact analyses of minerals, that if they were calculated 

 according to the determination which we have just given, they 

 would render an excess of silica necessary. But I must re- 

 mark on this head, that a mineral is rarely found of which si- 

 Mca does not form an essential component, which does not yet 

 contain from ^ to 2 per cent of it, and even more, either in the 

 state of quartz or in that of another siliceous mineral. This 

 circumstance must take place so much the more with the mi- 

 nerals which have silica for one of theii' elements ; and conse- 

 quently all that quantity of it which is found above what the 

 calculation gives should be attributed to a siliceous mixture 

 existing in the mineral. 



As to the number of atoms of oxygen contained in silica; 

 the new facts do not furnish us with the means of determining 

 this point. The circumstance that the carburetted silicium 

 produces when burned an equal weight of silica, leads us to 

 consider it as a quadricarburet, which by burning would give 

 an oxide at three atoms of oxygen ; but as I have notbeen 

 able to isolate the carburet of silicium, nor to burn it com- 

 pletely, this result, although obtained in several experiments, 

 and with silicium produced by different operations, has not 

 the certitude it ought to have, to be admitted as a proof. It 

 ought notwithstanding to be considered as affording a strong 

 presumption that silica contains three atoms of oxygen, so far 

 as our knowledge respecting the crystalline form of bodies fur- 

 nishes us with the means ot deciding on the number of atoms 

 of which oxides are formed. For the expression of the com- 

 position 



