-6- 
A mixture 
has the lowest 
containing 25 percent of jp^'-DDT and 75 percent of _o,p ! -l 
west setting point, namely 39.1°C. The setting point for 
DDT 
point for a 
mixture containing 70 percent of Pjj^-DDT is 86. 5-87. 2°, and for one 
containing 80 percent of pjp'-DDT 95.2°. A setting-point curve for 
mixtures of these two isomers is presented from which it is possible to 
ascertain the composition of any mixture from its setting point. The 
content of p.p'-DDT in technicel DDT as indicated by the setting point 
checks well with that obtained by recrystallization from alcohol. The 
solubility of pure _p,p*-DDT in alcohol at 30° is 1.6 gram per 100 ml. 
— Fleck and Preston ( 154 ) . This procedure was adopted by the U. S. War 
and Navy Departments (357 ) • 
DDT crystallizes in the orthorhombic system and has a density of 
approximately 1. The powder X-ray diffraction pattern was determined. 
—Clark and Cagle (113 ) • 
Composition of technical DDT 
Technical DDT, of setting point 88°C. as obtained in the Brothman 
continuous process, is* of the following approximate composition: 
jDjja'-Isomer (DDT) 
o,p*-l8omer •••••••••• 
o, o'-Isooer •••• • 
**0ily by-product" 
(unidentified) .... 
Peroent 
70 
18 
6 
Percent 
Unidentified solids... 2 
Volatile material .... 1 
Ash 1 
A material of higher setting point would contain a greater percentage 
of actual DDT. — tiunther (195 )* 
Attention is directed to the various isomers of DDT which may be 
present in variable proportions in different batches of material, and 
to the erroneous hypothesis that when DDT is dissolved in petroleum oil 
its surface tension is reduced. --Calif • Agr. Expt. Sta. ( 101 ) . 
Reactions of DDT 
DTTT prepared according to Zeidler*s procedure was dehydrochlorir.nted 
by boiling in alcoholic potassium hydroxide; the resulting ethylene prod- 
uct (m.p. 86-87 c 0.)was oxidized with chromic acid in acetic acid to p,p'- 
dichlorobenzophenone, which establishes the position of the chlorines as 
p,p' in DDT. Several attempts to oxidize p,p f «LrT with chromic acid in 
acetic acid to p,p , -dichlorobenzophenone gave no identifiable products. 
l,l-Di(j)-chlorophenyl)-l,2,2,2-tetrachloroethane (m.p. 91-92°) is readily 
made by chlorination of the trich lor o ethane compound or the dichloro- 
othylene derivative.- Urummitt et aJL. (190). 
