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sodium silioate 75 pounds and soap 1 pound per 100 gallons reduoed it 
to 0.027 grain per poundj washing with trisodium phosphate 10 pounds 
per 100 gallon?, reduoed it to 0.034 grain per poundj and brushing in a 
Trescott machine left the residue at 0.041 grain per pound.— Hough (217} . 
Preliminary tests at Vineennes, Ind., indicated that DDT residues 
on apples may be difficult to remove by either brush machines or flo- 
tation-type washers. Soaps, oils, wetting agents, and strong alkaline 
solutions had little effect, and none removed as much as half the resi- 
due. Similar tests at Yakima, Wash., confirmed these results. A 
maximum of approximately 60 percent of the DDT spray residue was re- 
moved by using 2 percent of oil in water followed by a wash in a wetting 
agent to remove the residual oil.— Baker and Porter (81). 
Two ounces of DDT per 100 gallons of oil, applied 4 times to July 17, 
produoed 0.0040 grain of DDT per pound on harvested Delicious apples, 
and 0.0045 grain per pound on Hubbardsons.~Cleveland (114). 
Washing tests indicate that it is difficult to remove DDT spray 
residues from apples and pears. Solvents commonly used for the removal 
of arsenical residues have no aotion on the DDT. Kerosene and heavier 
petroleum oils dissolve the DDT residue but redeposit it evenly in the 
oil film that remains on the fruit as it leaves the machine. Detergents 
appear to show greatest promise for removing DDT residues. In commercial 
washers the most effective results were obtained when apples or pears 
were processed in an overhead food machine, in which water (95°F.) con- 
taining a wetting agent such as Yatsol or Triton 720 was used. Residues 
of 0.111 grain of DDT per pound on apples were reduoed to 0.047 grain. 
Apples with 0.06 grain per pound were cleaned to 0.055 grain. Pears, 
however, that carried 0.042 grain per pound were cleaned only to 0.037 
grain. When the wetting agents were added either to acid or to sodium 
silicate, similar results were obtained. Silicate may prove more effec- 
tive for cleaning apples after they become waxy in storage.— Chi Ids and 
Robinson (ill ) • 
DDT residues on apples from experimental plots were as follows: 
Two samples from the Pacific Northwest, 2 and 7 p.p.m.; three samples 
from the Middle West, 5 p.p.m. each; and two samples from the East 4.5 
and 6 p.p.m.— U. S. Food and Drug Admin. (355) . 
DDT sticks to apples much tighter than does lead arsenate and is, 
therefore more difficult to remove. Apparently it goes into solution 
in the waxy covering of the apple. To remove the DDT it is almost 
necessary to take the wax off the apple. On the other hand, DDT does 
not build up so heavy a residue on apples as lead arsenate or the other 
insecticides used. Three cr four applications can be made without 
building up a serious residue.— Annand (74). 
