242 ^^ THE ALKALINi: METALLOIDS. 



first dissipates a portioYi of the water ; but in continuing the 

 application of it, the potash itself rises in vapour before tlie 

 whole of the water is expelled. Hence Berthollet found, 

 that potash in this state yields, when it is mixed with iron 

 filings, and exposed to a sufficiently elevated temperature, 

 a large quantity of hidrogen gas. From this it appears 

 evidently to contain water ; and from the results of its com- 

 bination with muriatic acid he infers, that the quantity 

 amounts to 13*64 in 100 parts of potash which has been 

 kept in fusion until it rises in yapour. 

 This apparent- Admitting this, it appears to lead to concluaions incom- 

 ble"^'^h t'h'' patible with the theory, which has usually been received, 

 theory of the of the decomposition of potash by galvanism. In ihii de- 

 decom posit ion composition oxigen is given out at the positive side, and 

 galranism, potassium appears at the negative side; and according to 

 the theory given by Mr. Davy of this experiment, this is 

 owing to the decomposition of the alkali— .the potassium ie 

 its base, and the oxigea the principle, with which this bast 

 had been combined, 

 as the water But if the existence of water in potash be admitted, the 



should be results are not conformable to this theory. This water, 

 decomposed, , .• i i i mi' • • r 



butnohidro- there can be little doubt, must sutler decomposition from 



gen is evoWed. the action of galvanism upon it, its oxigen will be evolved 

 at the positive pole, and its hidrogen ought to appear at 

 the negative side. TSo such evolution of hidrogen however 

 is to be observed in the common mode of making^the expe- 

 riments; and Mr. Davy, by whom it has been executed 

 with so much care, and on so large a scale, has remarked, 

 that at the negative surface there is no liberation of elastic 

 fluid, nothing being produced there but the metallic globules. 

 It appears therefore to follow almost as a necessary conclu- 

 sion, if the existence of water in potash be established, that, 

 since hidrogen does not appear in its insulated forrti, it must 

 enter into the composition of the metallic matter, which 

 appears at the negative side; and of course a different view 

 must be given of the operation from that which regards it 

 as a mere decomposition of the alkali. 

 Simplest mode Tliere are several modes of investigation, by which the 

 of iiiTcstigat inquiry with regard to this may be prosecuted. The sira- 

 irif this point. , * . , , , • , ,• t . , i 



plest experiment however, by, which light may be thrown 



OR 



