ARSENIC. 627 



ORDER VI. 



METALS ISOMORPHOUS WITH PHOSPHORUS. 



SECTION I. 



ARSENIC. 



Eg. 940.1 or 75.34 (470.04 or 37.67, Berzelius and Turner), As. 



This metal is found native, but more generally in combination 

 with other metals, particularly cobalt and nickel, and is largely 

 condensed, during the roasting of their ores, in the state of 

 arsenious acid. The metal may be easily obtained, in a state of 

 purity, by subliming a portion of native arsenic in a glass tube 

 or retort, by the heat of a lamp, or by reducing a mixture of 

 one part of arsenious acid and three parts of black flux, in the 

 same apparatus. The metal forms a crust, in condensing, of a 

 steel-grey colour and bright metallic lustre. It has been ob- 

 served to crystallize by sublimation in rhombohedral crystals, 

 and is isomorphous with tellurium and antimony. It is a brittle 

 metal, and very easily pulverised. The density of arsenic is 

 from 5.7 to 5.96. It rises in vapour at 356 (180 Cent.) with- 

 out first undergoing fusion. Arsenic vapour is colourless ; its 

 density is 10,370; and, like phosphorus and oxygen, its com- 

 bining measure is one volume. It has as strong an effect upon 

 the organ of smell as selenium : its odour resembles that of 

 garlic. Arsenic combines in three proportions with oxygen, 

 forming a grey suboxide by spontaneous oxidation in air, of 

 which the composition is undetermined, with arsenious and 

 arsenic acids, As O 3 and As O 5 . 



Arsenious acid, AsO 3 ; 1240.1 or 99.34. This compound is 

 also known as white oxide of arsenic, and is an abundant mer- 

 cantile product. It is in vitreous masses, as obtained by 

 sublimation, which immediately after sublimation are transparent 

 and colourless, or have a delicate shade of yellow, but gradually 

 become white and opaque, (page 153.) The density of the 

 vitreous acid is 3.7385, of the opaque acid, 3.699. Arsenious 

 acid sublimes at 380, without softening or fusing, forming a 

 vapour which is colourless and without odour. The density of 



