- 36 - 
filtration at 0° C was described ano illustrated. In case a rapid result 
was desired, instead of waiting for the carbon tetrachloride solvate to 
come to constant weight, it could be dissolved in ether, the solution 
evaporated, and the process repeated. This scheme sufficed to remove the 
carbon tetrachloricie completely, and the dried product was weighed as 
rotenone . 
Mei.jer (67) reported in 1958 that preliminary drying of the derris 
root sample at 50° and 80° C. caused a marked lowering in the rotenone 
results. Thus, a sample originally analyzing 10.6 percent of rotenone 
gave the following results after drying: 
TeraiDerature 
Time 
Eotenone 
'° C. 
Hours 
Percent 
40 
2 
10.3 
60 
2 
6.1 
80 
0.5 
6.2 
80 
2 
5.2 
The Imperial Institute (58_) reported in 1938 on work done by the 
Department of Agriculture of the Federated I'alay States. Soxhlet extrac- 
tion with carbon tetrachloride had been abandoned, and extraction with cold 
chloroform had been adopted as a routine method for rotenone. Results by 
this method fell only a little short of those by extraction with hot 
chloroform and were in agreement v/ith results obtained with hot ethylene 
dichloride and ethyl acetate. 
Graham (44) , in his 1937 report to the Association of Official Agri- 
cultural Chemists, described work on th^ determination of rotenone done 
in collaboration with Jones, and recommended that the chloroform extrac- 
tion method of Jones and G-raham (72) be adopted by the Association as a 
tentative method. 
A titrimetric step in the procediire for determining rotenone, mak- 
ing use of the rotenone-dichloroacetic acid solvate, was described by 
Jones (o?) in 1938. With dichloroacetic acid rotenone was found to form 
a solvate containing an equimolecular proportion of the two constituents. 
Formation of this solvate v/as adapted to determining the purity of the 
crude carbon tetrachloride solvate obtained in the usual gravimetric 
crystallization method. The method v?as briefly as follows: 
The carbon tetrachloride solvate obtained in the usual way 
is dissolved in acetone, and the solution is evaporated to remove 
carbon tetrachloride. The residue is dissolved by warming in 10 cc. 
of 60-percent dichloroacetic acid. Tne solution is cooled in an 
ice bath, 10 cc. of water is added slowly, and crystals of the 
dichloroacetic acid solvate are added for soeding. After the solu- 
tion h^s been 2 or 3 jf.inutas in the ice bath, water is added 10 
to 15 drops at a time, with cooling in the ice bath between ad.di- 
tions, until about 25 cc. has been added. Then 25 cc. more of 
water is added dropwise and finally, after further cooling, 50 cc. 
of water is added more rapidly. After some additional cooling the 
crystals are filtered on a Gooch and washed with about 250 cc. of 
