+> BULLETIN OF THE 
E(SWIC No. 259 
1 Contribution (rom the Bureau o( Animal Industry, A. D. Melvm, Chief. 
July 13, 1915. 
(PROFESSIONAL PAPER.) 
STUDIES ON CHANGES IN THE DEGREE OF 
OXIDATION OF ARSENIC IN ARSENICAL DIPPING 
BATHS. 
By Robert M. Chapin, Senior Biochemist, Biochemic Division. 
INTRODUCTORY. 
In the approximately four years during which arsenical dipping 
baths have been extensively employed for eradicating the Texas- 
fever tick in this country, and in the even longer period during which 
they have been put to similar use abroad, it has been discovered, along 
with other interesting and important facts, that the arsenic in such 
baths is prone to change its degree of oxidation. Arsenic is one of 
the considerable number of chemical elements which may be said to 
lead double lives; that is, they form two distinctly different series of 
compounds in which the element acts in many respects as if it were 
indeed two wholly different elements. Thus the element arsenic 
forms two oxids, first, arsenious oxid, in which two atoms. of arsenic 
are combined with three atoms of oxygen, and, second, arsenic oxid. 
in which two atoms of arsenic are combined with five atoms of 
oxygen. Both these oxids are essentially acid in nature; that is,j 
they readily combine with alkaline substances (bases) to form .salts. 
For example, when arsenious oxid is treated with sodium carbonate 
or sodium hydroxid there is produced sodium arsenite, while arsenic 
oxid, similarly treated, yields sodium arsenate. The common white 
arsenic of commerce is merely arsenious oxid. So when in the 
ordinary preparation of dipping baths, white arsenic is heated with a 
solution of caustic soda or of carbonate of soda, the resulting liquid 
is essentially simply a solution of sodium arsenite. 
Soon after arsenical dipping baths had come into extensive prac- 
tical use it was discovered that the sodium arsenite frequently 
seemed to disappear slowly with continued use of the bath. Thence 
it was only one step to discover that the element arsenic was in fact 
Note. — This bulletin will be of interest to cattle raisers who employ arsenical dipping baths in eradi- 
ating the Texas-fever tick. 
94290°— Bull. 259—15 
