12 



l]r>\VAIir) DTVETÎS. 



reuarded ;is frreativ exagü'eraied, if not eiToneou.s. Lastly, the 

 ca]()nu'l-"i\ ill"- \ai)i)iir.s are allowed to remain in eontaet witli tlie liot 

 iron of the ])ot instead of l)eiii,u' kei)t from it l)y the tliick lining of 

 earth provided in the Japane.se process, a contact which such va|)Ours 

 could not stand Avithout destruction. I think, tlierefore, that ^ve may 

 be foirlv doubtful whether any reliable description has yet been given 

 concerning the Chinese process, ^vhich Ave may expect to find to differ 

 little, il' at all, from the Japanese |)rocess, exce]»t in sali and alum 

 being used in ])]ace of the mother-li(pior of sea-salt, (jr ' water ' as Uno 

 Ranzan supposed it to be. 



Oiic thing, lo wliich atfeiition mav be called, isthat tlie Chinese 

 are! stated to add s(*me nitre to a simijai" niixtnre wlien empIoye<l to 

 «ive con<)si\e sublimate. For that luMUg tlie case, it is seen that tree 

 chlorine, whicli woidd here be develo])ed from the salt, nitre, and 

 alum, is necessary ibr the j-rcdiK'tion of the highei" chloride, and that 

 air and hydr<-chl('ric acid can only yield the lower cld<jride. a difference 

 of much theoretical interest, and indeed of ])racti<'al moment also. 



It is kiiown tliat re-snblimation of calomel generates some corro- 

 sive sulilimate. aiid, although aiithoi'ities are not (piite agreed as to 

 whether reaction occurs l)etween gold leaf and calomel va}»our, it is 

 liardlv to be doubted that such reaction does occur. Now I have 

 ibund tliat if in the Japanese apj'aratus the temperature of the cover 

 is raised sufficiently to volatilise much of th(; calomel, the remaining 

 calomel is no longer free from corrosixe sublimate. It must therefore 

 be borne in mind that the calomel formed in the Ja]'anese jti'ocess is 

 not, and cannot l)e, the result of true sublimation, Ijut of precipitatioii 

 as fist as formed from the tlu-ee gaseous bodies which give rise to it. 

 At the temperature at which mercury boils, calomel is either (piite 

 fixed or at most has a \apour of ex<'eedingly small tension. In the 

 two facts, that the three gases do not i-eact to vield corrosive sul)limate 



