INSECTICIDES AND REPELLENTS 13 



used is 68° F. A 5-percent solution w/v means that each 100 ml. 

 of solution contains 5 grams of the insecticide, and each gallon contains 

 0.416 pound. On a w/w basis each 100 grams of solution contains 5 

 grams of insecticide. If the solvent has a density of 0.82 gram per 

 milliliter (the approximate average for kerosene and light fuel oils), 

 and it is assumed that volumes are additive on dissolving, 5 grams of 

 chemical per 100 ml. of solution is equivalent to 5.16 grams per 100 

 ml. of solvent, 5.92 grams per 100 grams of solution, or 6.29 grams 

 per 100 grams of solvent. 



In most large-scale applications of DDT for the control of insects 

 affecting man, solutions in petroleum oils, such as kerosene and fuel 

 oils, are used. DDT is only slightly soluble in such oils, 4 or 5 percent 

 in refined kerosene and 7 to 11 percent in crude kerosene and fuel oils. 

 When a drum of the solution is being prepared, it should be closed and 

 rolled in the sun occasionally during the day. Before use the solution 

 should be examined for undissolved material by probing around in the 

 bottom of the drum with a long stick. If an open-top drum is used, 

 the mixture should be stirred until all the DDT is dissolved. Finely 

 ground DDT will dissolve in a few hours, with stirring, at summer 

 temperature. Mechanical agitators may be used to advantage. If 

 the DDT is lumpy or compacted, the lumps should be broken up and 

 the material passed through a 14- to 18-mesh screen. 



Petroleum oil solutions containing more than 5 percent of DDT 

 are obtained by adding suitable auxiliary solvents. To obtain a 

 10-percent solution, 10 percent of cyclohexanone or 15 to 20 percent 

 of xylene or other suitable solvent may be employed. An auxiliary 

 solvent may also be necessary to obtain a 5 -percent solution in refined 

 kerosene. A convenient method is to dissolve the DDT in a mini- 

 mum of the auxiliary solvent and then dilute to the desired concentra- 

 tion with petroleum oil. In the military-issue 20-percent airplane 

 spray (No. 24, table 3) DDT is dissolved in one of the approved 

 hydrocarbon solvents having a minimum flash point of 160° F. and a 

 distillation range of 365° to 750°. If lower concentrations are needed 

 and not otherwise available, this may be further diluted in the field 

 with fuel oil or kerosene to 5 or 10 percent. 



The standard 5-percent DDT spray (No. 23) contains 80 percent 

 of odorless kerosene and 15 percent of alkylated naphthalene having 

 a flash point of 150° F., a distillation range of 300° to 650°, and a 

 specific gravity of 9° to 22° API. The roach and ant residual spray 

 (No. 22) contains 5 percent of DDT and 2 percent of chlordane 

 dissolved in 78 percent of kerosene and 15 percent of alkylated naphtha- 

 lene with the same specification as above. A Federal space spray 

 (No. 26) contains 1 percent of DDT, 0.1 percent of pyrethrins, and 0.8 

 percent of piperonyl butoxide in deodorized kerosene. The kerosene 

 is specified to have a minimum flash point of 125° and a distillation 

 range of 350° to 500°. There is also a military specification (No. 25) 

 for an indoor fogging solution that contains 10 percent of DDT, 2 

 percent of lindane, 83 percent of trichloroethylene, and 5 percent of 

 SAE 50 motor oil. This is dispersed at the rate of 0.5 gallon per 

 100,000 cubic feet. 



The choice of a solvent depends on the method of application 

 and the insecticidal use. For airplane application, solvents of low 

 volatility are needed to reduce evaporation in the air. On the other 



