INSECTICIDES AND REPELLENTS 63 





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Figure 26. — Mass treatment of troops with a motor-driven duster for louse 

 control. (Courtesy of Capt. R. M. Alt man, U. S. Army.) 



Impregnation of Garments 



DDT is very effective and long lasting when used to impregnate 

 clothing. If the clothing is "treated in mass before issuance or dur- 

 ing laundering, the method largely eliminates the personal factor and 

 provides more permanent louse control than powders. Properly 

 impregnated garments remain effective through 6 to 8 launderings. 

 Troops provided with two suits of impregnated winter underwear 

 should remain free of lice during an entire winter, the season when 

 lice are most prevalent. In general, a dosage of DDT equivalent to 

 about 2 percent of the dry weight of the garment is recommended. 

 This dosage is 15 to 20 grams (0.5 to 0.7 ounce) for the regular issue, 

 winter-weight, 50-percent-wool underwear. 



Garments may be impregnated with DDT in a volatile solvent 

 or in an emulsion. In the first method the underwear is dipped 

 into a solution, such as a cleaning solvent containing the desired 

 amount of DDT, the excess solution is removed by wringing, and 

 the solvent is allowed to evaporate before the garments are worn. 

 This method is especially useful where dry-cleaning equipment is 

 available. In the second method a 25-percent DDT emulsifiable 

 concentrate (containing xylene as the solvent) diluted with water to 

 the desired concentration is used for wetting the garments. They 

 may be dipped individually in a pan or helmet, or by batches in a 

 larger container, such as a drum, or in laundry equipment. This 



