160 On the Genuinenefs and Parity of Drugs and Mtdicinas. 



Siveet Muriate of Mercury. Calomel, — ^Ph. L. 



Calomel ought to be perfe£lly faturated with mercury. Compleat faturation Can only be 

 known, by boiling for a few minutes one part of calomel, and -^ part of muriate of am- 

 moniac in lo parts of diftilled water. The fluid muft then be filtrated and examined by 

 means of carbonate of pot-afh. If the calomel is well prepared, no change will take place 

 oti the addition of this re-agent ; but if the preparation is imperfeft, a precipitate will 

 enfue, 47 parts of which indicate 48 of muriatic acid. 114 parts of calomel perfeftly 

 faturated with mercury, contain 97 of metal, and 17 of acid. It (hould be perfeftly ino- 

 dorous and taftelcfs, and when rubbed in a ftone mortar with ammoniac becomes intenfely 

 black. 



Red fulphiirated Oxide of Mercury. Redfulphurated ^ickftlyer. — Ph. L. 



The cinnabar of the fliops is generally adulterated with red oxide of lead, in order to make 

 it dry, fooner when ufed for oil painting, To difcover this reprehenfible focus, one part of 

 cinnabar is to be digefted by heat with four of acetic acid. If lead is prefent, thfe acid will 

 acquire a fweetilh tafte, and by letting fall into it a few drops of fulphuric acid, fulphate 

 of lead will inftantly be feparated. Genuine red fulphurated oxide of mercury fhould be 

 entirely volatile in the fire, and confequently leave nothing behind it after evaporation. A 

 compleat decompofition of its integrant parts {hould be effefted, by boiling one part of it 

 in twelve of nitro-muriatic acid, (compofed of three parts of nitric, and one of muriatic 

 acid) and then treating the refidue in a fimilar manner, with a fufficient quantity of foda, 

 or pot-afli, forced from carbonic acid. Cinnabar is likewife found adulterated with a mix- 

 ture of chalk and dragon's blood, and cinnabar thus contaminated, is of an exceedingly 

 fine cfimfon colour. If it contains carbonate of lime, an efFervefcence will enfue on mu- 

 riatic acid being added, and the earth will be taken up by the acid ; on adding diftilled 

 water, and feparating the fluid, chryftals of felenite will be obtained, on adding a little 

 fulphuric acid. The colouring matter may be compleatly extracted by digefting the refidue 

 in ardent fpirit, and fubfequent evaporation. 100 parts of Englifti cinnabar contain gene- 

 rally 20 parts of fulphur, and 80 of mercury. Its fpecific gravity is then 1000. 



Black Oxide of Mercury, ^ick/ilver with Sulphur. — Ph. L. 



This mixture of quickfilver and fulphur, ought to be at leaft fo far completed, that no 

 globules of mercury fhould be perceptible through a good microfcope. Its colour is then 

 of a beautiful black ; it is impalpable to the touch, and totally volatile by heat. It is found 

 fophifticated with ivory black. If this be the cafe, it will leave fome aflies behind when 

 laid on a red hot iron, or on ignited coals. If the mixture of the mercury with the ful- 

 phur has been well performed, the powder docs not give a white colour to gold, whea 

 rubbed on it for any confiderable time, nor can a feparation be eafily efiedled by faturating 

 it with a thick mucilage, &c. However, black oxide of mercury, which ftands thcfe tefts, 

 will not be found in commerce, nor can it reafonably be expe(^e<I< 



Nitrated 



