<240 SCIENTIFIC MEWS. 



The whole of these are verv 'perfect, and extremely well de- 

 fined. 



Lambeth, Feb. 22</. 1808* 



■■* *? * «• r 



SCIENTIFIC NEWS. 

 New mode of preparing Calomel, 



[E object of this process, invented by Mr. Joseph 

 Jewel, is to produce a cak.r.el, that shall always be in the 

 state of an impalpable powder. In the common mode this is 

 effected by grinding, or trituration, which is liable to 

 "be negligently performed 1 and Mr. Jewel, to prevent all. 

 danger of this, endeavours to obtain it in a powder uniformly 

 fine, by a particular manipulation in the last sublimation of 

 the calomel, which he describes as follows. 



I take calomel or mercurius dulcis, broken into small 

 pieces, and put it into an earthen crucible of the form of a 

 long bowl, so as to fill about one half thereof. I place the 

 crucible on its side in a furnace provided with an opening, 

 through which the mouth of the crucible projects about an 

 inch. I then join to the mouth of the crucible an earthen 

 ware receiver, having an opening at its side, to receive the 

 open end of the crucible. This receiver is about half filled 

 with water. I lute the joint with a mixture of sand and pipe 

 clay. The receiver has a cover, which cover has a side con- 

 tinued upwards for containing water, with a chimney or tube 

 in it, to allow the escape of steam from the water below. I 

 then apply a fire around the crucible, sufficient to raise the 

 calomel in vapours, and forced it through the mouth of the 

 crucible into the receiver ; where, by the water while cold, or 

 assisted by the steam when it becomes hot, it is instantly 

 condensed into an impalpable powder, possessing all the 

 qualities of calomel in its most perfect state. The calomel, 

 when thus prepared, is purer, whiter, and more attenuated, 

 than that obtained by grinding. It is proper to wash the 

 product over with water, before it is dried, to rid it of any 

 courser particles, which may form about the mouth of the 

 crucible. 



