1824.] M; Berzelius on Fluoric Acid. 453 



uncombined muriatic acid and muriate of barytes. If the same 

 experiments be made with the dilute acid which is washed from 

 the silica, a similar precipitation of the double salts is obtained, 

 but the remaining liquid uniformly gelatinizes when concentrated, 

 in consequence of the presence of the dissolved silica. Conse- 

 quently the gas is converted by the action of water into a liquid 

 acid, in which the fluoric acid and silica exist in the same rela- 

 tive proportions as in the insoluble double salts of fluoric acid 

 and silica with potash or barytes. This proportion, as will be 

 subsequently demonstrated, is such, that one-third of the silica 

 is separated and replaced by water. It is obvious, therefore, 

 that this acid can be obtained pure only when concentrated, and 

 that in proportion as the filtered acid liquid becomes diluted, the 

 greater will be the excess of silica which it will hold in solution. 



I consider these experiments to have demonstrated : 1st, That 

 in the gaseous silicated fluoric acid, the acid and silica contain 

 equal quantities of oxygen, that is, 3 atoms of acid are combined 

 with 2 atoms of silica; and 2dhj, That in the formation of the 

 liquid acid, one-third of the fluoric acid loses its silica, and com- 

 bines with water ; that is, it is composed of 3 atoms of hydrous 

 fluoric acid and 2 atoms of fluate of silica.* 



Water absorbs this gas at first with great avidity, but the pro- 

 cess becomes more and more tedious, in proportion as the mobi- 

 lity of the liquid is lessened by the deposition of silica. On 

 exposing to the gas a very small quantity of water, 01835 grm. 

 in a small balanced glass vessel over mercury, I found that 

 about 48 hours elapsed before absorption had completely ceased. 

 It had now entirely lost its fluidity, and smoked slightly when 

 exposed to the air. The increase of weight was 0*258 gramme ; 

 consequently 100 parts of water are capable of absorbing 140*6 

 parts of the acid gas, or, by abstracting the 27*65 parts of silica 

 which are deposited at the instant of the absorption, 1 12*95 parts 

 of the liquid acid. I have made many attempts, but unsuccess- 

 fully, to obtain the acid in its highest degree of concentration, 



* That the latter part of each of these enunciations may be understood, it may be 

 necessary to state that Berzelius considers fluoric acid to be composed of 1 atom of fluo- 

 ricum (70-34) + 2 atoms of oxygen ('200) = 270-3-I ; and silica, of 1 atom ofsilicium 

 (977) + 3 atoms of oxygen (300) = 5T7. The compound of fluoric acid and silica 

 which he styles the /luale, is that in which the acid and base contain equal quantities of 

 oxygen, or in which 3 atoms of acid are combined with 2 atoms of silica. A much less 

 complicated view of the constitution of these two compounds may be taken by consider- 

 ing, with Dr. Thomson, the atomic weight of fluoric acid to be represented by one-half, 

 and that of silica by one-third, of the numbers adopted by Berzelius. On this supposi- 

 tion, the gas would be composed of 1 atom of fluoric acid + 1 atom of silica ; and the 

 liquid acid, of 2 atoms of this simple fluate + 1 atom of hydrous fluoric acid. The for- 

 mula: by which Berzelius represents the composition of these two compounds arc S 9 F 3 

 and 3 F Aj* (- 2 S 9 F 3 . The formula by which they would be represented in confor. 

 mity with the numbers of Dr. Thomson, are $ F, and 2 S F + F Aj. 



