ORES OF ARSENIC 227 



3*35 — 3*65. Composition, sulphur 30, arsenic 70. Like 

 the preceding before the blowpipe. From Hungary, Bohe- 

 mia, Saxony, the Hartz, Switzerland, and Koordktan in 

 Asiatic Turkey. It has been observed in the lavas of 

 Vesuvius 



GENERAL REMARKS ON ARSENIC AND ITS ORES. 



Arsenic is most used in the state of arsenous acid, called also white 

 arsenic. This substance is prepared principally at Joachimstahl in Bo- 

 hemia, and in Hungary, and is obtained from arsenical cobalt and iron. 

 These ores are roasted in reverberatory furnaces, (the cobalt ores for the 

 cobalt they contain,) and the vapors (which are white arsenic) are con- 

 densed in a long horizontal chimney ; after undergoing a second subli- 

 mation, usually with a little "potash, it is ready for commerce. The 

 manufacture is very destructive to life, and those engaged in it seldom 

 live over 30 or 35 years. 



White arsenic, besides its use as a poison, is employed as a flux for 

 glass, and also to give a peculiar milky or porcelain-like hue to glass 

 ware. When too much is added, the glass becomes unsafe for domestic 

 use. 



The sulphurets afford valuable pigments. Orpiment is the basis of 

 the pigment called king's yellow. The ammoniacal solution of orpi- 

 ment is recommended for dyeing. It affords a yellow which is perma- 

 nent, but is injured by soap. Realgar is used in the preparation of the 

 pyrotechnical compound called white Indian fire, which consists of 24 

 parts of saltpeter, 7 of sulphur, and 2 of realgar, finely powdered and well 

 mixed. It burns with a white flame and great brilliancy. 



The sulphurets are obtained for commerce by distilling arsenical 

 pyrites and iron pyrites, (sulphuret of iron,) or from white arsenic and 

 rough brimstone ; the product is realgar or orpiment according to the 

 proportions employed. 



A combination of the arsenous acid with oxyd of copper, obtained by 

 mixing arsenite of potash and sulphate of copper, produces a fine green 

 pigment called Scheele's green. 



Arsenic is mixed in a small quantity (less than 1 per cent.) with lead, 

 in the manufacture of shot, as it renders the metal more ready to break 

 up into minute drops when caused to fall through a sieve from a height, 

 as in the shot tower, and the grains assume a more spherical form 

 on the descent, besides being less malleable than if of pure lead. In 

 shot towers, the melted lead falls usually about 150 feet into a vessel 

 of water at the bottom of the tower. They are afterwards sifted in 

 sieves of different degrees of fineness, from No. 1, the finest, to No. 12, 

 and thus the several sizes of shot are separated and assorted. There 

 are still some imperfect shot among them ; and to separate them the 

 shot arc made by a shake to roll from trays a little inclined into a bin ; 

 those that are imperfect roll sluggishly and are behind in the movement, 

 tond are thus separated to be melted over again. 



How do orpiment and realgar differ in composition ? From what ores 

 arseric obtained ? How is white arsenic prepared 1 For what in 

 *-senic used f How are shot made ? 



IMi 



