1825.] M, Berzelius on Silkium. 123 



portions, they are both constituted according to precisely the 

 same laws. 



Boracic acid has a more energetic affinity than silica for 

 fluoric acid ; nevertheless, it is incapable of producing a per- 

 fect decomposition of the fluate of silica. The gas obtained by 

 J. Davy's process is invariably contaminated with fluate of 

 silica ; and as my attempts to precipitate the silica from it by 

 means of boracic acid proved unsuccessful, I always prepared 

 the fluoboric acid which I employed in my experiments by dis- 

 solving boracic acid to saturation in pure fluoric acid. 



The methods which first occurred to me, as promising to 

 disclose the composition of fluoric acid, were, to decompose 

 the silicated fluate of potash or soda by boracic acid ; to mix 

 a solution of borax with fluoric acid, in the expectation of 

 converting the whole quantity of the borax into a double salt ; 

 or to combine fluoboric acid directly with saline bases ; but in 

 all of them I experienced a total failure. It only remained for 

 me to attempt the direct combination of a fluate with boracic 

 acid ; and by this synthetical process, I was fortunate enough 

 to attain my object. 



Borojluate of Potash. — This salt falls as a gelatinous precipi- 

 tate when fluate of potash is mixed with a solution of borate of 

 potash. By desiccation it assumes the form of a fine, mealy, 

 white coloured powder. Its taste is weakly bitter, but not at 

 all acid, and it does not redden litmus paper. It is anhydrous. 

 100 parts of cold water dissolve 1'42 part of the salt : boiling 

 water dissolves it in considerably larger quantity. It is slightly 

 soluble also in boiling alcohol. When ignited, it fuses and gives 

 off" fluoboric acid gas; but for complete decomposition it 

 requires a much longer continued and more violent heat than 

 the corresponding salt of silica. This salt is soluble in boiling 

 hot solutions of the alkalies and their carbonates, and as the 

 liquids cool, it crystallizes again unaltered. 



Borojluate of soda is more soluble in water than the acid 

 and neutral fluate of soda, and by slow cooling it crystallizes in 

 large, transparent, four-sided rectangular prisms. This salt 

 has a bitterish and weakly acid taste, and strongly reddens 

 litmus paper. It contains no water of crystallization. It is 

 sparingly soluble in alcohol. 



Borojiuate of Uthia may be prepared by precipitating the 

 borofluate of barytes with sulphate of lithia. It is very soluble 

 in water, tastes like the salt of soda, and crystallizes in large 

 prisms. In a moist atmosphere it deliquesces and runs to a 

 liquid. 



Borofluate of Ammonia. — When boracic acid is introduced 

 into a solution of neutral fluate of ammonia, it is instantly 

 dissolved ; ammonia is at the same time disengaged, and may be 

 detected by the smell. If no excess of acid had been employed, 



