-8- 
been slurried with water and then dried at 110°C. This treatment would 
destroy the oatalytic action if it were due to small traces of anhy- 
drous ferric, aluminum, or chromic chloride. Most solvents inhibit the 
catalytic decomposition of DDT by anhydrous ferric chloride, exceptions 
being nitrobenzene and chloroben2ene. With o-dichlorobenzene the cata- 
lytic action occurred even at room tejnperature«--Fleck and Ealler (163 ) ♦ 
Analytical methods 
A procedure for recovering organic chloride (DDT) spray deposits 
from apples consists in extracting 10 to 25 fruits with acetone or ben- 
zene and determining chlorine in the solution.-— Fahey (148 ) . 
DDT spray deposits on fruit or other material are removed with ben- 
zene, inorganic chlorides are removed from this solution by extraction 
with several portions of water, the benzene is removed by evaporation, 
and the DDT is decomposed by refluxing with 1 N alcoholic potassium hy- 
droxide for 30 minutes. The resulting potassium chloride is determined 
by titration. Recovery of known amounts of DDT by this method was 99.5 
to 101 ^percent.— Gunther ( 194 ) • 
Instructions are given for the determination of labile chlorine, 
total chlorine, and DDT by the Schechter and Haller coiorimetric pro- 
cedure. The ratio of labile chlorine to total chlorine on seven samples 
of DDT-sprayed apples from experimental plots in the western, central, 
and eastern apple areas ranged from 0.192 to 0.216, which closely 
approximates the theoretical 0.200* Recovery experiments wherein DDT 
was added in amounts equivalent to 1-15 p.p.m. to benzene extracts of 
unsprayed apples indicate that the over-all error of ohlorine methods 
(exclusive of the errors of sampling and sample preparation) is approxi- 
mately ^ 0.1 p.p.m. The errors at these levels affected the ratio of 
labile to total chlorine to the extent of about - 0.01. If the devia- 
tion from theory is greater than this, the sample should be subjected 
to further investigation.— U. S. Food and Drug Administration (353 ) * 
A coiorimetric method for the microdetermination of DDT is presen- 
ted. The test is based on the discovery that, when DDT is heated in an 
anhydrous pyridine solution containing xanthydrol and solid potassium 
hydroxide, a red color develops, which under proper conditions is pro- 
portional to the amount of DDT present. The reaction is sensitive to 
as little as 10 micrograms of DDT. It will detect small differences 
in concentration within the range of 10 to 200 micrograms. — Stiff and 
Castillo (338 ). 
Solvents for DDT 
The addition of 15 percent of a special methylated naphthalene 
[Velsicol] to kerosene makes a solvent that holds DTYT in solution at 
