82 VETEKINARY TOXICOLOGY 



papers coloured with arsenical pigments, although arsenic 

 may be found in the dust of rooms so papered. 



Arsenious oxide, arsenious acid, and its salts are by far 

 the commonest forms of arsenic. The oxide, crystalline, 

 vitreous, or amorphous, sparingly soluble in water and 

 volatile on heating, is the so-called ' white arsenic,' also 

 erroneously known as ' arsenious acid,' or simply as 

 ' arsenic,' of trade. The sublimed oxide forms charac- 

 teristic glistening octahedral crystals. Prom its likeness, 

 when powdered, to flour accidents have occurred. It enters 

 into the composition of certain rat powders, in which it is 

 often mixed with barium carbonate, flour, and blue. 



Of the salts of arsenious acid, copper arsenite is Scheele's 

 green, and a double copper arsenite and acetate is Schweinfurt's 

 green. 



The alkali (sodium and potassium) salts are easily soluble, 

 as also are the alkali thio-arsenites, in which oxygen is in 

 part replaced by sulphur. Alkali arsenites are used as 

 iveed-killers and wheat dressings, and a common sheep-dip 

 consists of alkali arsenite and thio-arsenite, along with 

 sulphur. Other dips are of alkali arsenite, soap, sulphur, 

 and sometimes iron sulphate. Dips usually contain about 

 20 per cent, of soluble arsenic and 3 per cent, of insoluble 

 arsenious sulphide, which is held to exercise a protective 

 effect during the intervals between dipping. After solution 

 for use the strength of soluble arsenic lies between 0'25 

 and 5 per cent. The arsenites are the most toxic of the 

 ordinary arsenical preparations. 



Arsenic acid, its oxide and salts, are less commonly met 

 with, and are less toxic, their action probably depending 

 on their reduction from the pentavalent arsenic to the 

 trivalent arsenious form. Sodium arseniate is sometimes 

 used as the poison of fly-papers. 



The common medicinal forms of arsenic are Fowler's 

 solution, which is a 1 per cent, solution of arsenious oxide 

 in 1 per cent, potassium carbonate, and liquor arsen. 

 hydrochl., which is a 1 per cent, solution of the oxide in 

 dilute hydrochloric acid. To these must now be added the 



