THE .MA\UFACTUJ;E of CALUMEL IX JAPAN. l\ 



is, as i« well known, p:irtly (.'oii verted into magnesia and liydrocliloric 

 acid. Hence the alkalinity of used iiiilsuchi. 



Tlie porosity of the walls of tlu' ai)[)aratus particnlarlv of the 

 layer of initsuclii on which the clay cup rests, nuist he more than 

 sufficient to allow enough air to enter during the working;-. I had 

 supposed that the hot hydrochloi'ic acid and air might, in contact with 

 the earth, have yielded a little chlorine, l)ut the temperature reached 

 in the process, normally worked, seems never to reach that required for 

 the liheration of chlorine. 



The Chinese process, if cürrectlij da^crihctU ditters from that used 

 in Jajian in several material [)oints, one of which is that the mercury 

 is intimately ground up with the other materials, and one fails io see 

 what reaction can take place 1)et\veen it and the two others, namelv, 

 salt and alum. Heated, the mixture must gi\e ott* mercurv and 

 hydrochloric acid, and then these as in the Japanese process will with 

 air give the cahmiel ; but this is independent of the previous intimate 

 mixture of the mercury with the salt and the alum. An(jther p(jint 

 is that in place of the magnesium chloride of sea-water as the source 

 oi' hydrochloric acid, the Chinese are said to use alum, or coi)peras. 

 which with the salt will react to give hvdrochloric acid. A third 

 point is that the cover is said to he closely liUcd to the \vo\\. poi , which 

 must nearly exclude the air, «without \\ hich it is impossil)le to explain 

 the formation of the calomel. Perhaps this is the reason whv the 

 C'hinese process is said to take four or ti\e hours tiring, since this mav 

 give time enough for the needed oxygen U) diffuse through the cup 

 and luting : ir will also account for the fact, if it is one. that the vield 

 of calomel is markedly less in weight than the nierciu-v used. Ai;-ain 

 there are to Ije noticed the statements that the ii'on [^ot is exposed for 

 hours to the strong heat of a charcoal fire, and that the hot clav cover 

 is cooled by throwing cold water <jn it, statements which must he 



