52 PYROMETALLURGY. [III. 



laboratory at Dresden (Arcliiv. d. Phar. xlvi. and Polytech. 

 Centralbl. 1847). 2Sb mercury is rubbed for 10 minutes with 

 J oz. of a solution of perchloride of iron (sp. gr. 1.48) and 

 ^ oz. water, the iron solution washed off with water, and the 

 mercury dried. If it contain more than 1 per cent, lead, the 

 operation should be repeated. Perchloride of iron has the 

 property of minutely dividing mercury, the iron being re- 

 duced to protochloride, and some subchloride of mercury being 

 formed, which prevents the globules from reuniting. AVhen 

 other metals are present, they are more readily chlorinized 

 than the mercury, and either washed away in solution or left 

 as an insoluble powder. To test the purity of mercury, Ulex 

 recommends shaking it in a clean glass tube, when, if impure, 

 a black powder appears on the surface of the glass. In this 

 manner ^oi^v part of lead is shown. Eisner offers as a con- 

 venient but more costly method of preparing absolutely pure 

 mercury, to warm a solution of corrosive sublimate (chloride 

 of mercury) in an iron vessel with iron nails. 



Mercury. — Violette (Comptes Rendus, 1850) has proposed 

 a very convenient method of distilling mercury by high pres- 

 sure steam. It consists in placing the amalgam or metal in a 

 cast-iron cylinder to which is attached a worm. This latter 

 serves as a heater for the water and also as a conduit for the 

 generated steam, which, in traversing the interior of the cylin- 

 der, heats and volatilizes the contained metal. The vapors 

 of metal and water, becoming involved, pass over in a double 

 current into the refrigerator, where they are condensed and 

 separate into strata. 



This plan has the great advantages of economy as to time, 

 fuel, and labor ; all danger of concussion is obviated, and as 

 there is no escape of vapor, the workmen suffer no injury to 

 health, as is the case by the usual process. 



Arsenic is associated with ores of cobalt, nickel, copper, 

 &c., as arseniuret of those metals, and in the preliminary 

 operations of roasting, it volatilizes as arsenious acid, and 

 condenses in flues and chambers constructed for the purpose. 

 It is then mixed with charcoal and sublimed as metal, or with 



