36 BEC0MPOSITION OV FLUORIC ACl®. 



product is solid, as in the preceding experiment, and i'S* 



formed of fluate of potash and silex. 



The fluoric gas It is now evident, that, since little or no hidrogen gas i» 



is en er e- eV olved on burning the metal of potash in fluoric acid gas, 

 composed, or » r . & . 



combines with this combustion cannot be ascribed to water- Hence in this 



potassium experiment either the fluoric acid is decomposed, or it com- 

 without oxid- / . . ...;■■. JL. , 



ng it. bines with the metal without oxiding it. These two hypo- 



theses being the only ones that can be formed, let us dis- 

 cuss them in succession. If it were the metal, that com- 

 bined entire with the fluoric acid, the probable result would 

 be a very inflammable compound, which with water would 

 give out as much hidrogen as the metal itself. But we ob- 

 tain only a third of what ought to be evolved. Besides, a 

 combination of this kind is contrary to all the facts on all 

 possible suppositions ; whether we consider the action of the 

 fluoric acid on the metals and alkalis, or the action of the 

 It is probably metal of potash on all the other acids. Hence we must 

 ecompose . conc i uc Je, that the fluoric acid is probably decomposed. 

 Consequently in this decomposition must be formed a com- 

 pound of the fluoric radical with potash and silex. It ap- 

 pears, that, when this radical is combined only with potash, 

 it is capable of decomposing water like the phosphurets ; 

 but that, when it is combined with potash and silex, it does 

 not decompose it, no doubt because this triple compound is 

 insoluble. 

 Potassium ea- j} e this as it may, it is extremely easy, to effect the com- 

 fluoric gas in hustion of the metal of potash in fluoric gas. When we 

 small quanti. would burn only a small quantity of the metal, the opera- 

 ie9 ' tion may be performed very conveniently over mercury in a 



little glass vessel blown by a lamp, to the top of which the 

 metal is conveyed on an iron rod, and which is heated by a 

 burning coal till the inflammation commences. 

 9t in large. But if we would burn large quantities of the metal, the 



operation should be performed in a jar holding about a 

 quart. This is first to be filled to within two fingers 

 breadths with fluoric acid gas. The metal is then to be 

 conveyed into it by means of an iron wire properly bent. 

 A small capsule, which may be made of a crucible by re- 

 moving a portion of the sides, being heated to a cherry red, 

 is then to be introduced, holding it in a pair of tongs ; and 



whe* 



