126 M, Berzelius on Silicium. [Aug. 



11'468, and 17-202 of oxygen: — numbers whose respective 

 ratios are 1:2:3. In the borate of ammonia which I ori- 

 ginally analyzed, the acid appeared to be combined with a 

 (quantity of base representing 34*4 of oxygen, which is six 

 times the lowest degree of combination. 



From the analysis of native borate of magnesia, M. Arfwedson 

 deduced the saturating capacity of the acid to be 16*83, that is, 

 very nearly 17*2. In the crystaUized borate of potash, prepared 

 from boracic acid and carbonate of potash, the saturating 

 capacity of the acid proved to be 6'7, and when anhydrous 

 boracic acid was fused with carbonate of potash, and the loss 

 of weight in carbonic acid determined, it was found that 100 

 parts of boracic acid had combined with 139 parts of potash, 

 whose oxygen amounts to 23*51. By a similar experiment 

 with carbonate of soda, it was found that 100 parts of acid 

 had combined with 135*5 parts of soda, which contain 34*66 of 

 oxygen. These experiments therefore gave the following satu- 

 rating capacities : 



5*734 in the biborates of potash and of soda. 

 11*468 in borax, and in neutral borate of ammonia. 

 17*202 in boracite, and in borate of ammonia. 

 22*93 in subborate of potash. 

 34*40 in subborate of soda and of ammonia. 



On comparing these numbers, we find that they are multiples 

 of the lowest by 2, 3, 4, and 6. 



Two methods presented themselves for a determination of 

 the composition of boracic acid ; namely, either an investigation 

 of the relative proportions in which it combines with fluoric 

 acid, or direct synthesis by the oxidation of boron. For the 

 first of these, the analysis of the borofluates of barytes and of 

 potash appeared to me most suitable. 



100 parts of the salt of barytes yielded 10*5 parts of water, 

 and 67*2 parts of sulphate of barytes = 44*10 per cent, of 

 barytes. 150 parts of the salt of potash yielded 103*8 parts of 

 sulphate of potash = 37*417 per cent, of potash. 



My direct experiments on the oxidation of boron (to be 

 related hereafter) rendered it probable that boracic acid con- 

 tains 68*81 per cent, of oxygen ; and this composition would 

 correspond accurately with the analysis of the double salts, if 

 we suppose them to be constituted in such a manner that the 

 fluoric acid contains four times, and the boracic acid three tiines, 

 the oxygen of the base, or, in other words, that the boracic 

 acid is combined with thrice as much fluoric acid as the al- 

 kaline base. 



To verify this composition, I dissolved in water 250*6 parts 

 of crystallized bicarbonate of potash and 154*66 parts of crys- 

 tallized boracic acid (the (juantities which, according to tho 



