t2& M. Berxelius an Siliciwk^ [Airfei 



The horojiuates are produced when in this compound the 

 water is replaced by any other base, and they are so consti- 

 tuted, that the base is associated in them with four times as much 

 ^fluoric acid as in the neutral salt, and with a quantity of boracic 

 acid, which contains thrice as much oxygen as the base. These 

 salts, therefore, contain an atom more of fluoric acid than the 

 corresponding combinations of siHca. 



I now proceeded to give a final confirmation to these con- 

 clusions, by determining the quantity of oxygen which is ab- 

 sorbed by boron during its acidification ; but after having made 

 txial of various processes, I found it impossible to prepare boron 

 in a state of such absolute purity, that the composition of 

 boracic acid could by means of it be determined with more pre- 

 cision than by the indirect methods already described. The 

 most successful experiment which I was able to make was one 

 in which 0*036 gramme of boron was converted by ignition in a 

 current of oxygen gas into 0*091 gramme of boracic acid, and 

 according to which boracic acid ought to contain 61 '5 per 

 cent, of oxygen ; but the boron here employed was contami-* 

 uated with carbon, whose volatilization during the combustion 

 would necessarily cause the apparent augmentation of weight 

 to fall short of tfie truth. 



Boracic Acid, and Fluate of Silica. — Silicated fluoric acid gas 

 is not affected by dry boracic acid, biit it is instantly absorbed 

 by the crystallized hydrate* The product is a true chemical 

 combination, in which the boracic and fluoric acids are so 

 proportioned that they contain equal quantities of oxygen, and 

 m which the fluoric acid is divided equally between the boracic 

 acid and the siHca. This substance does not smoke when 

 exposed to the air, as would happen, were it a mere mixture 

 offluoboric acid and sihca. Water decomposes it, and disen- 

 ga^s about three fourths of the silica. 



Fluoborates. — By this appellation I propose to designate the 

 double salts, in which a single base exists in combination with 

 boracic and fluoric acids. They appear to be produced when 

 the foregoing compounds are saturated with the base, and to 

 be capable of existing irt a variety of proportions between the 

 fluate and borate. I nave not examined any of them minutely i^ 

 at present, they possess too little interest^ to induce one to en- 

 counter the difficulties Vyhich would attend aij*l6^4et determi- 

 nation of the proportions of the two acids. • ' '^ ^ " \"\ ^^ 



Boron. — The easiest and most economical 'rtfetftdtt-'^pfe-/ 

 paring boron, is to decompose an alkaline bbrcifliffA^^bJ fWi^^ 

 sium. Boracic acid, even by protracted fu^iorlj ca'nfndbljd 

 completely deprived of water, and it absorbs ' 1tfn ttdtfittoh^r 

 quantity during pulverization; this is the cAtise why tH^'V^i 

 auction of boracic aoid is accompanied -by a rather vidlelit^^fet^-* 

 nation, and why a portion of the mixture is in genert^l prfetj^^a* 



