AW Tuhlicatiom. ^77 



acid; and an exccfs of lii^ie, by ^ white precipitate, onblow* 

 jng air, from the lungs, through the foiqlion, by means of a 

 tobacco-pipe." 



*^ Mercury or Quichjilver — Hydrargus, P. L, 

 ♦^ Scarcely any fubftance is fo liable to adulteration as 

 inercur)', owing to the property which it pofTcfl'es of diffolv- 

 ing completely fome of the bafer metals. This union is fo 

 (Irong, that ^hcy even rife along with the quickfilver when 

 diHillcd. The impurity of piercury is generally indicated by 

 its dull afpe^l; by its tarn idling, and becoming covered with 

 a coat of oxyd on long expofure to the air, by its adhcfion to 

 the furfcce of glafs ; and, whfjn fliaker^ with water in a bot- 

 tle, by the forrnation of a black powder. Lead and tin are 

 frequent impurities ; and the mercury becomes capable of 

 taking up more of thefe, if ?inc or bifmuth be prpvioufly 

 added. In order to difcover lead, the mercury may be agi- 

 tated with a Httle water, in ofder tp, oxvdale that metal. 

 Pour off the water, and digeft the mercury with a little acet- 

 pus acid. This will diflblve the oxyd of lead, which will be 

 indicated by a blackifh precipitate with fulphuratcd water. 

 Or, to this acetous folution, add a little fulphat of foda, which 

 will precipitate a fulphat of lead, containing, when drv, 

 73 per cent, of metal. If only a very minute quantity of 

 lead be prefent in a large quantity of metal, it may be de- 

 tefted by folution in nitric acid, and the addition of fulphu- 

 ratcd water. A dark brown precipitate will cnfue, and will 

 fubfide, if allowed to {land a few days. One part of lead 

 may thus- be feparated from 15,263 parts of mercur}'. Bif- 

 nuith is detpcled by pouring a nitric folution, piepared with- 

 out heat, into diftilled water; a white precipitate will appear, 

 if this metal be prefent. Tin is manifefted, in like mannex, 

 by a weak folution qf nitro-muriat of gold, which throws down 

 a purple fediment; and zinc, by cxpofmg the metal to heat.'* 



*^ Moih' of dcU^lhig the Adulteration of Poiijjhesy VcarlaJJ.'cSy 



and Barilla, 



^' Few objects of commerce are fophifticatcd to a greater 



extent than the alkalies, to the great lofs and injury of the 



{j|eacher, the dyer, the glafs-maker, the foap-bolle.rj and of 



9 aJJ 



