PREPARATION AND PROPERTIES OF COLEOIDAE 
ARSENATE OF LEAD 1 
By F. J. BrinlEy, Assistant Entomologist , Fruit Insect Investigations, Bureau of 
Entomology, United States Department of Agriculture 
INTRODUCTION 
During the early work on the control of the Japanese beetle (Popillia 
japonica Newm.), commercial arsenate of lead apparently had a decidedly 
repellent effect upon the insect. For this reason experiments were 
undertaken by B. R. Leach and the writer to determine whether the 
repellent action was due to the physical properties of the arsenate or to 
some other factor. Among the series of experiments made to determine 
this point the writer made a study of the preparation of colloidal lead 
arsenate. The work reported herein was performed by the writer at 
the Japanese beetle laboratory at Riverton, N. J., during the season of 
1920-21. 
CHEMICALS USED 
An arsenate of lead composed of very fine particles may be prepared 
by the chemical action of lead nitrate with disodium arsenate. How¬ 
ever, when these chemicals react in the presence of a protective colloid, 
such as gelatin, a colloidal arsenate of lead may be formed. 
The chemicals used for the preparation of colloidal lead arsenate are: 
Lead nitrate (Pb(N 0 3 ) 2> disodium arsenate (Na^jHAsO^HjO), and 
sheet gelatin. According to Haywood and McDonnell 2 the chemical 
reaction between lead nitrate and disodium arsenate largely results in 
the formation of acid lead arsenate (PbHAs 0 4 ): 
Pb(N 0 3 ) 2 4 - Na 2 HAs 0 4 = PbHAs 0 4 + 2NaNQ 3 . 
In all probability the gelatin does not enter into the chemical action, 
but is adsorbed by the particles of lead arsenate as they are formed and 
seems to prevent the individual particles from uniting and forming 
larger ones. 
Other colloids, such as gum arabic, dextrin, and potato starch, were 
used but did not prove as satisfactory as did the gelatin, because a 
large amount of the material was required to give the same results as 
a much smaller quantity of gelatin. 
The formula found to be the most satisfactory and the one used by 
the writer is as follows: 
Lead nitrate. 331-4 g m - 
Disodium arsenate. 3 1 1. 96 gm. 
Gelatin. 17. 35 gm. 
The gelatin is added to the crystals of sodium arsenate and the mixture 
is dissolved in a small quantity of hot water and diluted to make 10 liters. 
The lead salt is likewise dissolved in hot water and diluted to make 
1 Accepted for publication Aug. n, 1933. 
* Haywood, J. K., and McDonnell, C. C. lead arsenate. U. S. Dept. Agr. Bur. Chem. Bui. 131, 
p. 17. 1910. 
Journal of Agricultural Research, 
Washington, D. C. 
ahq 
(373 > 
Vol. XXVI, No. 8 
Nov. 24, 1933 
Key No. KL-1X5 
