1825.] M, Berzelius on Silieium, 125 



acid at 74*17 per cent., and its saturating capacity at 37'085. 

 These numbers are founded upon my analysis of borate of 

 ammonia, and of the crystallized hydrous boracic acid. The 

 more recent analysis of L. Gmelin and Arfwedson, led me to 

 distrust the accuracy of these determinations, and I attempted 

 to reproduce a borate of ammonia, similar in constitution to 

 the one which I originally analyzed. But all my trials with 

 this view proved unsuccessful, and I suspect therefore that 

 some error had been committed in determining the weight of 

 the specimen employed in my first analysis. 



To determine the composition of borax, I dissolved it in a 

 mixture of the fluoric and sulphuric acids, and evaporated the 

 solution to dryness ; 2*634 grammes of the fused salt, decom- 

 posed by this process, yielded 1*853 gramme of sulphate of 

 soda. 100 parts of borax contain therefore 69*173 parts of 

 boracic acid and 30*827 parts of soda. The crystals, by fusion, 

 lost 47*1 per cent, of water. According to these experiments, 

 the crystallized salt is composed of 



Boracic acid . . 36*59 



Soda 16*31 oxygen 4*1715 



Water 47-10 41*889 



The oxygen of the water is obviously 10 times that of the 

 base. The proportion of the soda would probably be obtained 

 most accurately by computation from that of the water, both 

 because the latter is susceptible of a more rigid analytical deter- 

 mination than the former, and because any error in the quan- 

 tity of the water would induce a corresponding error of only 

 one-tenth the amount upon that of the soda. The composition 

 of borax, according to this calculation, would be 



Boracic acid 36*5248 .... 100* 



Soda 16*3753 .... 44*8336 



Water 47*1000 



These 44*8336 soda contain 11*4684 oxygen, which number 

 indicates the saturating capacity of boracic acid in all the salts 

 proportional with borax. The acid also must contain oxygen 

 in some multiple of 11*4684. 



M. Arfwedson analyzed no fewer than three distinct combi- 

 nations of boracic acid and ammonia. His results were as 

 follows : — 



^ . ., (1) (2) (3) 



^ Boracic acid 64*0 63*34 55*95 



Ammonia 7*9 12*88 21*55 



Water.. 28*1 ....23*78 ....22*50 



In these salts the boracic acid is combined with quantities 

 of ammonia which are equivalent, in other bases, to 5*734, 



