oti different Comlinations of Fluoric Add. 377 



b<'en removed. The precipitate of fluat of lime was sepa- 

 rated by filtration. The filtered liquid was evaporated to 

 dryness ; and the amnioniacal salt heated in a platina cru- 

 cible till it was entirely dissipated. The residue had th^ 

 appearance and taste of quicklime. It was dissolved iii 

 acetic acid, and the solution yielded sulphat of lime on the 

 addition of sulphat of ammonia. The liquid was evaporated 

 to dryness, and when the residuum had been heated to 

 dull redness, nothing remained but a little white powder, 

 weishnig about a grain, and having all the properties of 

 gypsum. Thus it appears that silicated fluoric acid gas 

 contains no alkali. 



My next object was to ascertain the composition of com- 

 mon liquid fluoric acid — that acid obtained by the decom- 

 position ot silicated fluoric acid gas by water, and which, 

 on account of the separation that occurs of part of the silex, 

 may with greater propriety be called subsilicated fluoric 

 acid. For this [)urpose, 43*21 cubic inches, barom. 30*4, 

 tht rm. 50, or 44 cubic inches at common temperature and 

 pressure, were successively added, two cubic inches at a 

 time, to one cubic inch of distilled water in a small jar 

 over mercury. The whole of this, the gas being pure, 

 was readily condensed. The temperature was somewhat 

 raised. The sllex precipitated, formed a gelatinous 

 mass of a blueish colour, which had absorbed all the 

 water like a sponge, so (hat none appeared fluid. This 

 gelatinous mass was carefully transferred to a filter, and 

 washed with distilled water till it was rendered insipid, and 

 incapable of reddening litmus paper. It retained its blueish 

 hue only whilst moist. When dried and ignited, it was in 

 thin lamellaj, and of a snow-white colour, and surprisingly 

 bulky. It weighed 7'33 grains, and was found to be pure 

 silex. Thus it appears that the subsilicated fluoric acid 

 formed by the decomposition of 44 cubic inches of silicated 

 fluoric acid gas contains 7*33 grains of silex less than the 

 gas itself. Consequently independent of water, which no 

 doubt is essential to this acid, 100 parts of it seem to con- 

 »ist of 54"36 silex 



45*44 acid 



100-00 

 I have endeavoured to ascertain what quantity of silicated 

 fluoric acid gas a given quantity of water will condense. 

 In one instance -^,>^^ of a cubic inch of distilled water ab- 

 sorbed 51 cubic inches, barom. 30*5, therm. GO''. The gas 

 was added to the water in ajar over mercury, as fast as it 

 was absorbed. The experimciit was stopped, when the 



gas. 



