ARSENIC. 307 



colour, and volatile, exhaling the odour of garlic. It is distinguished 

 from pharmacolite (arseniate of lime) by its solubility in water. 



Sp. 5. Arsenical Cobalt, or Cobalt Pyrites. Pl. XLIII. 

 fig. 5. — This properly belongs to a distinct genus, and consists of 

 oxide of arsenic combined with cobalt and sulphur. It is divided 

 into three varieties, from its colour, viz. tin-white, silver-white, 

 and grey cobalt. It occurs massive, in various particular forms, 

 and its lustre is metallic. It is from this ore that the cobalt of 

 commerce is principally obtained. 



The term Arsenic is commonly applied to what has been ascer- 

 tained to be an oxide of a peculiar metal j but in the language of 

 chemistry it is appropriated to the metallic base of this compound 

 alone. To obtain this metal the oxide mixed with half its weight 

 of black flux, is exposed to heat in a crucible, another crucible being 

 inverted over it and luted to it ; the carbon of the black flux com- 

 bines with the oxygen of the oxide, and forms carbonic acid, while 

 the metal is sublimed, and condenses in a crystaline form in the 

 upper crucible. Metallic Arsenic is of a blueish or steel -grey 

 colour; it has considerable lustre, and is extremely brittle and 

 pulverulent. It tarnishes quickly by exposure to the air, and 

 becomes black. It is volatalized at 356° of Fahrenheit, in dense 

 -white fumes, which have a strong smell of garlic ; at a higher tem- 

 perature it burns with a blue flame. Metallic Arsenic exerts no 

 action on the animal system, but when oxidized it is a very active 

 poison. 



White Oxide of Arsenic Arsenici Oxidum, Ph. L., or 

 Arsenious Acid, (called arsenic in the shops,) is principally brought 

 from Bohemia and Saxony, where it is extracted in large quantities 

 during the roasting of the ores of cobalt and arsenical pyrites. The 

 ore is thrown into a furnace resembling a baker's oven, with a long 

 flue, or horizontal chimney, into which the fumes pass, and are 

 condensed into a greyish or blackish powder. This is refined by a 

 second sublimation in close vessels, with a little potash to detain 

 the impurities. The oxide of arsenic thus obtained is in the form 

 of a dense white semi-transparent mass ; sometimes it is opaque, 

 pulverulent, or in the form of needles, in which state it was for- 

 merly called/towers of arsenic. It is inodorous, and its taste is gene- 



