124 M, Berxelius oh Silicium, fArcl 



the salt obtained by evaporating the solution is the borofluate 

 of ammonia. It is undoubtedly remarkable that in these circum* 

 stances the boracic acid should be capable, like a base, ofdis- 

 placing ammonia ; but such is the operation of the combined 

 affinities. 



The dry salt may be sublimed without undergoing decom- 

 position. Its taste resembles that of sal-ammoniac, and it 

 reddens litmus paper. It is largely soluble both in water and 

 in alcohol. 



This salt is of a different constitution from the compounds 

 which are produced by the neutral condensation of fluoboric 

 acid and ammoniacal gases. 



Borojiaate of bari/tes is most readily obtained by adding 

 carbonate of barytes in small quantities at a time to dilute 

 fluoboric acid, until it ceases to be dissolved. By spontaneous 

 evaporation of the solution, it crystallizes in four-sided rec- 

 tangular prisms. This salt posseses an acid reaction, but its 

 taste resembles that of the barytic salts in general, and is not 

 in the least degree acid. In a temperature above 104°, it 

 effloresces, and loses its water of crystallization. Alcohol de- 

 composes it into a soluble acid salt and an insoluble pulverulent 

 compound, whose composition I have not examined. The 

 crystals contain 10-34 per cent, of water, whose oxygen is 

 therefore double that of the barytes. 



Borofluate of Lime. — A gelatinous mass, which has an acid 

 taste, and reddens litmus paperi 



Borofluate of magnesia is very soluble in water, and shoots 

 during evaporation in large prismatic crystals. Its taste is 

 bitter, like that of the other salts of magnesia. 



Borofluate of alumina and borofluate of yttria are only soluble 

 in water when assisted by an excess of acid ; and by slow eva- 

 poration of the solution, they may be obtained in crystals. 



Borofluate of oxide of lead shoots by spontaneous evaporation 

 in short, four-sided, apparently rectangular prisms or tables, 

 resembling the crystals of the borofluate of barytes. Its taste 

 is at first sweet and astringent, but it finally leaves an impres- 

 sion of acidity. Both water and alcohol decompose it into an 

 acid and a sub-salt. 



Borofluate of oxide of zinc may be prepared by dissolving 

 zinc filings in fluoboric acid. It is uncrystallizable and deli- 

 quescent. 



Borofluate of oxide of copper is very soluble in water, and 

 yields by evaporation a mass of bright blue-coloured acicular 

 crystals, which are excessively deliquescent. 



I come now to the investigation of the constitution of these 

 compounds ; for which, however, a knowledge of the saturating 

 capacity of boracic acid is indispensable. 

 . In, my chemical tables, I have estimated the oxygen of boracic 



