J 6a .On tht Genuinenefs and Purtly ifDfUgi and MedicintS. 



black coal behind, and the latter fophiftication is detefled by expofing it to heat in an open 

 Tefiel, and reducing the rcfidue by means of a little charcoal to the metallic ftatc, for far- 

 ther inveftigation. 



Red Oxide of Mercuvj. Calcined ^ikhjilver. — Ph. L. 



Is feldom found adulterated. If well prepared it is totally volatile by fire. It is folublc 

 in fulphuric, nitric, and muriatic acid, but the acetic, oxalic, malic, and tartareous acids 

 have no efFeft upon it. 



Corroftve Muriate of Mercury, Muriatid ^liclfdver. — Ph. L. 



It has been faid that this produdl has been found adulterated with arfenic. Though thic 

 may probably feldom be the cafe, yet when it is fufpedted, one part of the corrofive fubli- 

 mate may be diffblved in 24 parts of diftilled water, and precipitated again- by carefully 

 adding a folution of carbonate of pot-afh. The white precipitate thus afforded, is then 

 feparated from the fupernatant fluid. This fluid thus freed from all the mercury it con- 

 tained, is then to be tried by means of the ammoniate of copper. A tranfparent blue liquid 

 will be formed, if the corrofive muriate of mercury was free from arfenic ; but a yellowifli 

 green precipitate will appear if arfenic was prefent. This precipitate collected, dried, and 

 laid on ignited coals, will foon diffufe the garlic fmell peculiar to that metal. Two hun- 

 dred and fixty-feven parts of this precipitate, contain one hundred and fixty-two parts of 

 copper, and one hundred and fixty-five of arfenic. 



Sixty-nine parts of corrofive muriate of mercury contain, if well prepared, generally 50 

 parts of mercury, 17 of folid muriatic acid, and two of watei: of cryflalization. One part 

 is then foluble in fixteen parts of cold water at 50", in 3-I- of boiling water, in 2i of col(J 

 ardent fpirit, or in a little more than its own weight, of boiling ardent fpirit. 



Iron. Iron. — Ph. L. 



The iron filings of the (hops, which in general are procured from the gun-fmiths, and 

 other artificers, are never free from copper or brafs. If fome of the filings be difTolved in 

 pure muriatic acid, and a poliflied iron be immerfed into this faturated, and concentratcti 

 folution, the part of the metal in contadt with the fluid, will foon become coppered, if the 

 quantity of this metal was confiderable. A fmaller quantity of copper is manifefted by 

 digefting the iron filings, in water impregnated with ammoniac, which will acquire a 

 blueifh hue, if the filings contain copper. But the beft way to deteft the minuteft quan- 

 tity of copper or brafs is, to difTolve one part of the fufpefted iron in three of nitric acid, 

 and to decompofe this folution by the addition of carbonate of pot-afh, or ammoniac freed 

 from carbonic acid. In the firfl cafe, a greenifli precipitate, and in the latter, a blue folu» 

 tion will be obtained, particularly if the ammoniac is added in abundance. 



The prafticc^ of purifying iron filings ufually made ufe of in the fhops, by means of a 



magnet, is not fo perfect as is generally cxpeiSed. When other metals have been united 



with 

 2 



