Dr Davy's Experiments oti Silicated Fluoric Acid Gas. 243 



or probably will be, supplied by any extension of experiments of 

 the same kind as those referred to ; which can only be attempted 

 with a prospect of definite results when we shall have attained a 

 far more intimate knowledge of the structure of bodies than we 

 now possess, and in which every consideration of probability, as 

 far as we can judge, would rather discourage the idea of any 

 extension of the analogy of the relation which subsists between 

 the colour of surfaces, and the efiects of luminous heat upon 

 them, to the case of simple heat unaccompanied by light. 



— ■■ ' ,/jt i .. r !i ;i i:v n j >^ii. ' 



Notice (f some Experiments on Silicated Fluoric Acid Gas. 

 By John Davy, Esq. M. D. F. R. S. Assistant Insp€|2tQf i}f 

 Army Hospitals. Communicated by the A uthp^. ^ , t ^ j . .; . 



The results which I now beg leave to communicate to the 

 JRoyal Society, wer^ obtained in experimenting on silicated flu- 

 oric acid gas, with the hope of acquiring further information re- 

 specting the fluoric principle. 



Of the unsuccessful experiments the slightest notice may suf- 

 fice, — such as of the sublimation of phosphorus and sulphur, 

 and of iodine, in the acid gas ; the fusion of zinc, — the heating 

 to redness of iron and charcoal in it, and also of the chloride of 

 calcium ; the exposure of it to the sun's rays mixed with hy- 

 drogen ; and the decomposition by heat, in a retort filled with 

 this gas, of the chlorate of potash. In each of these instances, 

 no efiect whatever was produced on the gas, as had been before 

 found in several of them, both by MM. Gay Lussac and The- 

 nard, and also by my brother, the late Sir Humphrey Davy. 



On the most probable hypothesis, that silicated fluoric acid 

 gas is a compound of a principle analogous to chlorine, and of 

 silLcium, it appeared not unreasonable to expect, that the fluo- 

 rine, even in combination with silicium, might expel oxygen from 

 lime and the other earths, for the bases of which it appears to 

 have a powerful affinity ; or, if not, that the acid gas might com- 

 bine with these bodies directly. 



The first trial I made was on lime ; the result was remark- 

 ^^, When perfectly caustic, lime was introduced into a warm 



