84 FLUORIC ACID. 



the-case, a solution of nitrate of lime was added to the ammo* 

 niacal solution neutralized by nitric acid, from which the silex 

 in the preceding experiment had been removed. The preci- 

 pitate of fluat of lime was separated by filtration. The filtered 

 ^liquid was evaporated to dryness j and the ammoniacal salt 

 heated in a platim crucible till it was entirely dissipated. The 

 residue had the appearance and taste of quick lime. It was 

 dissolved in 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 has been 

 heated to dull redness, nothing remained but a little white 

 powder, weighing about a grain, and having all the properties 

 of gypsum. Thus it appears that silicated fluoric acid gas 

 contains no alkali. 

 Common My next object was to ascertain the composition of common 



ac ij liquid fluoric acid— -that acid obtained by the decomposition of 



silicated fluoric acid gas by water, and which, on account of 

 the separation that occurs of part of the silex, may, with 

 ar subsilicat- greater propriety, be called subsilicated fluoric acid. For this 

 ed fluoric acid. p urpose ^ 4321 cubic inches, barom. 304, therm. 50, or 44 

 cubic inches at common temperature and pressure, were suc- 

 cessively 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 tem- 

 perature was somewhat raised. The silex precipitated, formed 

 a gelatinous mass of a blueish colour, which had absorbed all 

 the water like a sponge, so that none appeared fluid. This 

 gelatinous mass was carefully transferred to a filter, and 

 washed with distilled water till it was rendered insipid and inca- 

 pable of reddening litmus paper. It retained its blueish hue 

 has lost more on ^ wn, ^ st mo * st « When dried and ignited, it was in thin 

 than one fourth lamellae, and of a snow-white colour, and surprisingly bulky. It 



of its silex by we ;gh e( j 7*33 grains, and was found to be pure silex. Thus it 

 uniting with ° ' 6 l 



water. appears that the subsilicated fluoric acid formed by the decom- 



position 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 consist of 



54*56 silex 



