ON THE ALKALINE METALLOIDS. SGT 



iny potassium in solution, is expelled, it would deserve to 

 ]^e made the subjecl of experiment whether the metal ob- 

 tained is precisely the same with the metal procured when 

 there is no sensible disengagement of hidrogcn ; though still 

 it is possible, that in all cases a portion of the hidrogen of 

 the water in fused potash may be disengaged, which becomes 

 only more evident when a large quantity of the alkalis 

 is decomposed by a powerful galvanic battery. It can scarce- 

 ly however be supposed, that the whole of the hidrogen is 

 disengaged, else it must be apparent, if the above obser- 

 vations be just, even in the experiment where the weakest 

 power is employed, for the volume of elastic fluid to be 

 disengaged at the one side, if the watqr is decomposed (and 

 of this decomposition scarce a doubt can be entertained) is 

 as large as that disengaged at the other. 



In the method of procuring potassium by the action of When potas- 

 iron on potash, at the temperature of ignition, a disen-J'"j.^j^^P^j^^^^jjg 

 gagement of hidrogen gas takes place during the process ; a of iron, the hi- 

 fact which may be supposed to prove at least, that the ^^^^^jJ^^^JJ^^ 

 whole hidrogen of the water contained in fused potash does that portion 

 not enter into the composition of the potassium which that^l'^^^^^™^'^"^^ 

 potash yields. This may, perhaps, be admitted; it is pos- 

 sible, as I liave already remarked, that a portion only of 

 the hidrogen exists in the potassium. Yet in drawing this 

 conclusion one circumstance is to be attended to. The 

 greater part of the base of the potash is obtained, not in. x 



sulated, but in combination with iron. The hidrogen of 

 this latter portion may be expelled, the iron combining 

 with the real metallic matter, and this may afford the greater 

 part of the hidrogen that is disengaged, 



1 Potassium has an affinity to hidrogen. It combines with Compounds of 

 that gas so as to form an elastic compound; and, according PPJ^^'^^""^^"*^ 

 to the experiments of Gay-Lussac and Thenard, it alsomed. 

 combines at a high temperature with a large quantity of hi^ 

 drogen, and forms a solid substance of a light gray colour, 

 from which hidrogen is disengaged by the action of water. 

 Mr. Davy was unable to obtain this result; but these che- 

 mists, aware of the objection he had made to their experi^ 

 ment, have more lately repeated it, and have affirmed, thal^ 

 when potassium is heated in hidrogen gas, a quantity Jo/ the 



gas 



