BUREAU OF ENTOMOLOGY AND PLAN T QUARANTINE 109 
Two bibliographies on cyanide compounds used as insecticides were 
issued in mimeographed form. 
ACCESSORY MATERIALS FOR USE WITH INSECTICIDE 
The study of wetting agents was continued. Measurements of sur- 
face tension, and of the tension existing between solutions of the 
agents and a standard mineral oil, were made for over 200 proprie- 
tary products as a means of surveying their relative value as surface- 
tension depressants, this depressing action being the most important 
characteristic of a substance to be used as a spreader with insecticides. 
A new method of getting further evidence on this characteristic was 
developed, which consisted in titrating a solution of a given wetting 
agent with distilled water or artificial hard water until the surface 
tension was reduced to a pre-seleeted figure. 
Because phenothiazine continues to show promise as an insecticide 
against the codling moth, the effort to find an adhesive capable of 
retaining it upon apples was resumed. Evidence was obtained of 
some favorable action by several proprietary products, by freshly 
precipitated aluminum hydroxide, by aluminum silicate, and by wet 
grinding of certain mixtures. 
Various oxides of iron were studied as possible correctives for the 
injury to crops grown in soil treated with white arsenic, in an attempt 
to adapt that insecticide, which is cheaper than lead arsenate, to 
the control of Japanese beetle grubs. No special value could be 
demonstrated. 
The study of powdered diluents for use with sodium arsenite in con- 
trolling the Mormon cricket was continued, special attention being 
paid to a commercial product consisting of pyrophyllite from which 
it was possible to obtain a considerable fraction of coarse material, 
which previous studies indicated to be desirable for use with the very 
coarse sodium arsenite being employed. 
The wetting and spreading properties of mixtures of sodium carbon- 
ate with n-caproic, n-caprylic, n-capric, lauric, myristic, and palmitic 
acids were investigated. For aqueous mixtures of sodium carbonate 
with 1.0 percent of fatty acid, the surface tension, interfacial tension 
against mineral oil, and spreading coefficient, when plotted as func- 
tions of the alkali-fatty acid-mole ratio, give curves that are similar 
in form with few exceptions. The relative positions of the curves 
correspond approximately with the order of increasing molecular 
weight of the fatty acid. The characteristics of the carbonate mixtures 
are similar to those of the corresponding hydroxide mixtures, with 
some differences which are apparently accounted for by the diacidic 
nature of the carbonate. The oleate mixtures have exceptional prop- 
erties which help to explain their excellence as detergents. 
In a study of inorganic salts as adjuvants for increasing wetting 
power, tests were made with a sulfonated ester of a dicarboxylic acid. 
Addition of chlorides of calcium, magnesium, or sodium to solutions 
of this wetting agent produced significant increases in wetting power, 
as measured by surface tension or by spreading coefficient on mineral 
oil. The improvement was so substantial as to indicate that this effect 
may be of practical importance in the formulation and use of these 
materials. 
