BULLETIN OF THE 
No. 76 
Contribution from the Bureau of Animal Industry, A. D. Melvin, Chief. 
April 29, 1914. 
(PROFESSIONAL PAPER.) 
LABORATORY AND FIELD ASSAY OF ARSENICAL 
DIPPING FLUIDS. 1 
By Robert M. Chapin, 
Senior Biochemist, Biochemic Division. 
INTRODUCTION. 
The use of arsenical dipping fluids for the treatment of cattle 
infested with Texas-fever ticks is increasing. A mixture termed by 
the Bureau of Animal Industry "standard arsenical solution" is pre- 
pared from white arsenic, sal soda, and pine tar, and is largely used 
for both official and private dipping operations. Proprietary dipping 
fluids also have appeared on the market to some extent. Previous 
publications 2 of the bureau contain directions for the preparation of 
"standard arsenical solution/' together with general information of 
importance to users of arsenical dips. 
During the last few years wide practical experience of the bureau 
with all kinds of arsenical dips in the field has shown with increasing 
forcefulness that one of the greatest obstacles to the successful use of 
these preparations, and consequently to the effective prosecution of 
the tick-eradication work now progressing so well over considerable 
areas, lies in the uncertainty attached in many cases to the composi- 
tion of these dips. There is no doubt that arsenical baths, properly 
prepared and used, are very effective tickicides and cause little 
injury to cattle. But the Texas-fever tick is a resistant organism. 
Destruction only follows its immersion in rather strong solutions of 
arsenious oxid, so strong in fact that if made only a little stronger 
the cattle themselves will begin to show effects. That is, the margin 
of safety within winch solutions of this violent poison may be satis- 
factorily used is rather narrow. Too little fails to kill the ticks; too 
much injures the cattle. In either case the cause of tick eradication 
i A popular account of laboratory tests for actual arsenious oxid and for total arsenic, together with 
methods of field assay for dips used in tick eradication. Of special application to officials and others con- 
cerned with the analysis and control of these preparations. 
2 Farmers' Bulletin 498; Bureau Animal Industry Circular 207. 
29207°— 14 1 
