120 eOMBIKATIONS OF OXIMURIATlC GA8 AND OXIGEN. 



The common It is evident from this chain of facts, that common potash 



i ^^ ' and soda are hydrate, and the bodies formed by the coin** 



bustion oF the alkaline metals are, as I have always stated, 



pure metallic oxides, (as far as our knowledge extends) free 



from water*. 



I shall 



may be referred to tlie acid. 95 grains of soda, ignited to whiteness 

 in a platina crucible, with 140 of dry flint glass, lost 22-2 grains j 80 

 gtains of boracic glass were added to this mixture j a fresh efferves- 

 cence took place, and after intense ignition for a few minutes, there 

 was an additional loss of weight of four grains and a half. The energy 

 with which water adheres to certain bodies in other cases is t<hown by 

 the experiments of Mr. Berthollet, Ble/n. d^ArcueU^ torn, ii, page 47. 

 Indeed it is impossible to say, that a neutral compound, or a fixed 

 acid, is ever entirely free from water ; it is only the first proportion* 

 that are easily separated. If the proportions of water in common pot- 

 ash and soda were to be judged of from their loss of weight, in com- 

 bining with boracic acid, it would appear to be from 19 to 20 per cent 

 in the first, and from 23 to 25 in the second. 

 Potassium and * After the experiments detailed in my last two papers, it may per- 

 sodiumnothy- ]japs appear unnecessary, at least to those enlightened British che- 

 mical philosophers, who have closely followed the progress of science, 

 to offer any new evidences to prove, that potassium and sodium are 

 not hydrurets of potash and soda; particularly as Messrs. Gay-Lussac 

 and Thenard, the ingenious advocates of this notion, have acknow- 

 ledged, in the Moniteur to which I have before referred, that it '\& not 

 tenable j but on a subject so intimately connected with the most re-, 

 fined departments of chemical philosophy, and with so many new ob- 

 jects of research, aoditioual facts cannot be wholly devoid of use au^ 

 application. 



Mr. .J)alton, \n the second volume of the work which he entitles 

 ** A Niw System of Chefriical Pfiiinsopkt/,*' of which he has had the 

 goodness to send me a copy, has, I find in his fii*Kt pages, adopted 

 the idea, that potash and soc'a are metallic oxides ; but in the latter 

 pages has considered them as simple bodies, and the metals formed 

 from them as compounds of potash and soda with hidrogen. He has 

 piven no facts in favour of this change in his opinion : his principal 

 arf^uDtent is founded upon the process in which I first obtained potas- 

 sium* Common potash is a hydrat : when oxigen is procured from this 

 by Voltaic electricity at one surface, and potassium at the other surfacej 

 Mr. Dalton, conceiving that this oxigen arises from the water, states, 

 that the hidrogen of the water must eombine with the potash to forn^ 

 potassium. It is evident, that, adopting such a plan of reasoning, lead 

 jfcod copper might be proved to be hydrurets of their oxides; for Mheu 

 these metals are revived from their aqueous acid solutious, oxigen is pro- 

 duced at the positive surface, and no hidrogen at the nejjative surface. 



