,~)S ANNUAL REPORTS 01 DEPARTMENT 01 AGRICULTURE, 1951 
of a study on the utilization of agricultural wastes as diluents 
carriers for insecticides. Samples, experimental data, test methods, 
and other information were exchanged with ;i company that is experi- 
menting in the development of vegetable materials as carriers for 
insecticides used in dusting wheal and other grains in storage. Car- 
riers for ilif purpose should resemble the natural components of the 
unprocessed grain in order to avoid down-grading due to flavor, health 
hazard, or appearance. Particular attention was given to the bal- 
ance between particle fineness and dustability and between adhesive- 
ness i" grain and ease of removal in cleaning. Tentative specifica- 
tions were prepared for botanical carriers. The most important waste 
or surplus product- were evaluated as to their suitability and avail- 
ability. Ranked in their approximate order of importance, the most 
outstanding prospects arc: Wheat waste, corncobs, English walnut 
shells, rice nulls, almond shells, peanut hulls, potato flour, and potato 
starch. Some already arc being used by insecticide manufacturers. 
New Analytical Procedures for Insecticide Residues Developed 
A colorimetric method has been developed for the determination of 
methoxychlor in milk and fat- in amounts a- low as 5 micrograms. 
The met 1 1 owe Id or is separated from t he butterfat of the milk or other 
fatty material by dissolving the fat in //diexane ami extracting the 
solution several times with nitromethane. The nitromethane extract 
containing any met hoxychlor present i- evaporated to remove the sol- 
vent. The residue i- nitrated with fuming nitric acid and the nitrated 
product Is treated with sodium methylate to produce a color, which 
i- measured wit h a colorimeter. 
Another colorimetric procedure ha- been worked out for the deter- 
mination of pyret hrins in paper bags that have been impregnated with 
pyret hrum for protection against insect attack. As little as 200 micro- 
grams of pyrethrins can he determined quantitatively. The method 
can he adapted to amount.- a- -mall a- 25 micrograms with somewhat 
|r— accuracy. The impregnated paper i- extracted with 95-percent 
ethyl alcohol. Water is added to the concentrated alcoholic extract, 
and it. in turn, is extracted with petroleum ether. The petroleum- 
ether solution is evaporated, the residue is taken up in 95 percent 
ethyl alcohol, and hydroxyl amine hydrochloride and alkali arc added. 
The solution is then treated with hydrochloric acid and ferric chlo- 
ride. The resulting color is measured with a colorimeter. 
A method previously developed by Bureau chemists for determin- 
ing minute amounts of organic phosphorus compounds based on their 
cholinesterase-inhibiting properties proved unsatisfactory for the 
determination of parathion because tin- insecticide is low in inhibit- 
ing properties. I>\ continued study it ha- hern found possible to 
adapt this method for the determination of parathion by first oxidiz- 
ing the parathion to its oxygen analog, giving a product which is a 
-t rong inhibitor. 
New Nicotine Combinations Selected (or Field resting 
Twelve of the new combinations of inc. tine and other materials 
found most promising in exploratory tests were selected for more 
exten ive field testing. The exploratory tests were conducted over 
