the Humid Way- — General InJlruBkns, 5 



futphur, with a few drops of water, and triturated the whole until the mercury had entirely 

 combined with the reft of the mixture. I then added water, and began the evaporation, 

 agitating the mixture continually with the peftle. The brown colour began towards the 

 end of the evaporation to brighten, and at laft changed to the colour of bad fealing-wax, 

 conftantly inclining to brown. Forefeeing that if I continued the evaporation I fliould 

 rifk a fecoud obfcuration of the colour, I placed the cup which contained the mixture on 

 a ftove which had been heated. At that time I totally defpaired of correfting the 

 colour of cinnabar fpoiled at ths firft evaporation ; but having infpe£ted my cinnabar at 

 the end of two hours, I faw with pleafure that the colour had become finer as the mafs be- 

 came thicker. I triturated it in the cup with the addition of a few drops of water, and 

 repeated this operation five or fix times in the courfe of the day. At the end of 24 hoUrs, 

 my cinnabar was very thick and very good. , I added mote water, and left the colour on 

 the ftove for three days ; at the end of which the cinnabar had acquired the utmoft bril- 

 liancy, and was equal to the fineft fpecimens of Mr. KirchofF, excepting that in which he 

 had obtained a fliade of carmine, as I have already remarked. After repeating this experi- 

 ment with fuccefs with one pound of mercury, thirty-five drams of flowers of fulphur, and 

 ten ounces of cauftic alkali, I found reafon to make the following general obfervations upon 

 this procefs : 



It is neceflary for the production of cinnabar, 



1. That the mercury fliould be perfe£lly mixed with the flowers of fulphur ; for which 

 reafon, after having triturated it with the peftle in a glafs mortar, with the addition of a 

 fmall quantity of cauftic alkali to moiften it, it muft be levigated upon porphyry, or fuch 

 Other hard ftone as cannot mix its particles with thofe of the cinnabar, becaufe every 

 foreign fubftance is highly prejudicial to the beauty of the colour. If the quantities ope- 

 rated upon exceed one pound, it will be neceflary to procure a mill for grinding colours 

 which muft alfo be of a filiceous ftone. The mixture upon a levigating ftone is evidently 

 tec expenfive for a manufafluring procefs in the large way. 



2. The beft vefl"els for evaporating the mixture are thofe of porcelaine, or the yellow 

 ■ware of England. The peftles ought to be glafs. 



3. The heat of a fand-bath is fufficient to this operation. The heat of ebullition is not 

 neceflary •, but at the beginning, particularly when there is much liquid, the heat muft ap- 

 proach as nearly as poflible to that of boihng. 



4. The receptacle in which the fand is placed muft be deep enough to admit the whole 

 of the porcelaine or earthen veflel in which the cinnabar is produced, to be plunged there- 

 i», and environed by an equal atmofphere of heat. The fand round the vefll-l need not 

 exceed the thicknefs of a full inch. 



5. The mixture muft be perpetually ftirred : otherwife the mafs will fubfide by its weight, 

 and become clotted -, a circumftance which it is eflential to avoid. 



6. A certain degree of thicknefs is requifite during the operation, in order to afll)rd a 

 good colour •, but great care muft be taken not to fufl^er the mafs to become too thick 

 and more particularly the agitation muft be ftrongly kept up at thefe periods of con* 

 denfation. 



7. Though it is poflible to obtain from the fand-bath a very beautiful cinnabar which 

 may be immediately edulcorated, yet it is much more prudent and advantageous not to 



fuiTcj- 



