ARSENIC. 185 



Arsenious oxide is frequently used in the arts and for manu- 

 facturing purposes, as, for instance, in the manufacture of green 

 colors, of opaque white glass, in calico-printing, as a powerful 

 antiseptic for the preservation of organic objects of natural his- 

 tory, and, finally, as the substance from which all arsenic com- 

 pounds are obtained. 



The officinal solution of- arsenious acid, Liquor acidi arseniosi, is a 

 1 per cent, solution of arsenious acid in water to which 2 per 

 cent, of hydrochloric acid have been added. 



The officinal solution of arsenite of potassium, Liquor potassii 

 arsenitis, or Jfowler's solution, is made by dissolving 1 part of 

 arsenious oxide and 1 part of potassium bicarbonate in 95 parts 

 of water and adding 3 parts of compound tincture of lavender ; 

 the solution contains the arsenic as potassium arsenite. 



Arsenic oxide, As 2 5 (Arsenic; pentoxide, Anhydrous arsenic acid). 

 When arsenious oxide is heated with nitric acid, it becomes 

 oxidized and is converted into arsenic acid, H 3 As0 4 , from which 

 the water may be expelled by further heating, when arsenic 

 oxide is left : 



2H 3 AsO 4 = As 2 O 5 + 3H 2 O. 



Arsenic oxide is a heavy, white, solid substance which, in 

 contact with water, is converted into arsenic acid. This acid 

 resembles phosphoric acid not only in composition, but also in 

 forming metarsenic and pyroarsenic acids under the same con- 

 ditions under which the corresponding phosphoric acids are 

 formed. The salts of arsenic acid, the arseniates, also resemble 

 in their constitution the corresponding phosphates. 



Arsenic oxide and arsenic acid are largely used as oxidizing 

 agents in the manufacture of aniline colors. 



Disodium hydrogen arseniate, Sodii arsenias, Na 2 HAs0 4 .7H 2 = 



311.9 (Arseniate of sodium). This salt is made by fusing arsenious 

 oxide with carbonate and nitrate of sodium : 



As 2 3 + 2NaNO 3 + Na 2 CO 3 = Na 4 As 2 O 7 + N 2 O 3 + CO 2 . 



Sodium pyroarseniate is formed, nitrogen trioxide and carbon 

 dioxide escaping. By dissolving in water and crystallizing, the 

 officinal salt is obtained in colorless, transparent crystals : 



Na,As 2 7 + 15H 2 O = 2(Na 2 HAsO 4 .7H 2 O). 



