on: potassium and sodiuki. (y(y 



fonned tuy the muoa of potu,Sih a^id hidroge»,). WQjild l>p 

 done away with at once. 



Will:i respeift tf> Mr. Divltou's second ifica, that the bi- Rcmarlcs oa 

 <1 rate of potash hi the <;»inbHvrel expevLuuiit seems to be ^=^^-<^^"af- 

 (lerompose<l partly H»to jxjtash and, wafer, aiid partly into 

 ])ottassium tuid oxv:>;e0 : wl^t i^ ^^^ powec or tUIipJ^'s 

 Avhich produces this mised deco»:ij position ? Mr. Dojtouha^ 

 told ns, p. 470 ;»i»d 47 1, thnt at a red heat potash remain* 

 in traiiqnil i'lision — " but if the heat be ificreased, white 

 " fumes be'j;in to arise c^i.ion^!y^ The (Oknli and water 

 *' hotli evaporate in thi^^ ease — therefore the process caun^t 

 •* be used to expel the last portion of water from the jjI- 

 ** kali." — It ii not thereCore according- to biniself Xhetein^ 

 peraiure of the " intensely heated iron tube,** nor its con- 

 tents, tliat separate the tcaicr fro.iu the potash. We are 

 speak ini( of the water of course in its imdecompoundetl 

 state, — ^^Mr. DaltoiVs wordi^ ^^y (as stated above) " ipto, 

 j)otash and water". 



Mr. T3alton calls the potash »sed by th^Freuch Clieiivi-sts 



in the I'oregoing nitthod ofdecompositioii, the^r5^ hydrate^. 



laeanin*;, i suppose^ that which consists of 1 particle of water 



+ 1 of potash, or, in phln Englishy potash containing' \6 pec 



cent of water, which is exactly the potash oUaiaed by heat*, 



ing any other hydrate, containing more water, to redness, 



and which cannot, according to hiuiself, be farther deprived 



of its water by heat, What then, i ask again, is the power, 



that produces this separation of tvnivr and potash ? Iroij 



licatcd to whiteness will decompose water, we know t'ef^f ^ ' 



well, but not that it will se[)arate it, nndeconi posed, from 



potash. But how does Mr. I>avy explain the fact? Ac- Mr, Daw's 



cordiuLj: to him, the aftinitv of iron for oxigen, and of '^,''1'^'^"^''®" **^ 



,. . , • ' , , ,. , • , . ^^^^ "^ case, 



iron tor potassium, renders it capaiile ox taiuug the oxigen 



both from the potash, and tlie water it coiitidns; and iri 

 this it is assisted by the affinity of hidrogen for potassium^ 

 which at a high temperature is capable of dissolving it in 

 large quantities, but dej)Osits it again on cooling. This, 

 in few words, is Mr. Davy's explanation of the decom- 

 position of potash by the gunbarrel. The reader may 

 tind it more amply detailed in a note of that Gentleman tc^ 

 his Bakerian Lecture, in the Philosophical Tiansaetion* for 



