1825.] M. Berzelius on Silicium, 127 



above supposition, represent an atom of each of the two sub- 

 stances), and added to the mixture as much fluoric acid as 

 rendered it slightly acid. The solution, after having been 

 concentrated, was found to contain no excess either of potash 

 or of boracic acid, and when evaporated in a water-balh, it 

 yielded to the last drop borofluate of potash. This was, there* 

 fore, the real constitution of the double salt. 



We are now entitled to deduce the following conclusions 

 with respect to the composition of the boracic and thefluoboric 

 acids, and of the fluoborates. 



Boracic acid contains six times as much oxygen as the soda 

 with which it is combined in borax, that is, 68*8104 per cent. 

 It is capable of combining with bases in such proportions, 

 that its oxygen amounts to 12, 6, 4, 3, and 2 times the oxygen 

 of the bases, and as in these combinations the multiples 12 and 

 6 occur far more frequently than any of the others, it appears 

 highly probable that boracic acid contains 6 atoms of oxygen, 

 and that the salts whose constitution is proportional with that 

 of borax, are neutral borates. On this supposition, an atom of 

 boron weighs 271*96, and an atom of boracic acid 871*96. 

 The nun^erical composition of boracic acid is 



Boron 31*1896 100*00 



Oxygen 68*8104 220*62 



The crystallized boracic acid contains, according to my 

 early experiments, 44 per cent, of water, of which it loses 

 one half' when exposed to a temperature above 212°, and the 

 second half when combined with a different basis. It follows 

 from this that boracic acid is capable of combining in two pro- 

 portions with water ; and that in the first of these compounds 

 the water contains as much oxygen as the acid ; but in the 

 second, only half that quantity. The numerical composition of 

 these two hydrates is 



Boracic acid 1 atom .... 72*1 ; 1 atom . , , . 66*38 



Water 3 27*9; 6 43^62 



Fluohoric acid, on the hypothesis that fluoric acid is an 

 oxygen acid, is so constituted, that the two acids contain 

 equal quantities of oxygen ; that is, it consists of an atom of 

 boracic acid and 3 atoms of fluoric acid. Its numerical com- 

 position is 



Fluoric acid . ; 47*942 



Boracic acid 52*058 



When fluoboric acid gas is absorbed by an excess of water, 

 one-fourth of the boracic acid is disengaged : the compound 

 thus formed consists of an atom of hydrous fluoric acid and aa 

 ^tom of fluoboric acid. 



