- 29 - 
HotenoDS added per 5 gm. Hotenone found 
(as pure rotenone) ("by ether method) • ' ' ■ 
Grain Gi*am , . • 
0.3451 
.0713 
.0683 
.0348 
\. ' .0378 
They. stated that when less than 0.0355 gm. of rotenone was" employed 
values w.ere too low. Determinations /by chloroform extraction (5-gm. 
sample) and crystallization from carton tetrachloride on some of these 
prepared samples, as well as on samples of Serris and IJundulea, gave 
results in good agreement v/ith those "by ether. 
Levallois (82) in 1937 said that ethyl acetate and chloroform were 
tne two hest extraction solvents for use in, the determin'^.tion of rotenone. 
He emphasized that all trace of extraction solvent must' ha eliminated 
under vacuum, before crystallizing from carbon tetrachloride. Levallois 
stated that . the tendencj^ was to abandon the colorimetric methods in favor 
of the gravimetric methods for rotenone. 
• Crystallization methods for rotenone were said by Schonberg ( llO ) 
to be open to the objection that they were not applicable to very small 
amounts of rotenone , that the results were not in accord with the in- 
secticidal activity, and . that they were very laborious. It was stated 
that the carbon te.trachloride complex contained variable proportions of 
impurities and ths^t its content of pure rotenone could not be deduced. 
Colorimetric methods were recommended. 
^orsley (l3l) in 1937. stated that prior to the publication of the 
work of Cahn and Boem,(l3) he had found that addition of pure rotenone 
to extracts of I.!undulea suberosa bark resulted in a considerably greater 
net yield of rotenone. He obtained hi.'jher yields of rotenone by adding 
decolorizing charcoal to the powdered bark before extraction with ether. 
It was necessary, however, to increase the time of extraction and better 
extraction solvents were tried. Percolation with hot ethyl acetate gave 
the most satisfactorv results. Details of this method have been described 
(130). 
Eowaan (107^) in 1937 recommended the use of. chloroform at room 
temperature for the. extraction of rotenone. he stated that drying at 
50° G. for 1 hour brought the rotenone-carbon tetrachloride solvate to 
constant weight. Rovraan tentatively reccramended determination of the 
purity ,by alcohol recovery, although he said that this process needed im- 
provement . 
., .Heijer (86)>,in! 1937, before a meeting of the Euitenzorg (.Tava) 
Experiment Station stai'f , .discussed the evaluation of derris and reviewed 
methods for. the. determination of rotenone. Treatment of the mother liquor 
from rotenone separation by chromatographic adsorption, by formation of 
the hydrazine of rotenone, and by other methods, was said to show as much 
