- 30 - 
additional rotenone as 10 percent of the remaining extract. Of three 
methods of determining piirity alcohol recovery was said to give the lowest 
values, the melting-point method the highest, and the polarization method 
intermediate values. Because of ease of handling the last two were pre- 
ferred. 
A method for rotenone usini"- ethj'l acetate for extraction was sug- 
gested "by Pozzi-ilscot (97) in 1937. Extraction wa"B accomplished "by 
boiling under refliox. The extract, concentrated to a sirup, was treated 
with sufficient activated charcoal to make a dry powder and then extracted 
with a known vclvune of carbon tetrachloride already saturated with rotenone, 
This extract was diluted with carbon tetrachloride if necessary. The 
extract was made to the original volume of the carbon tetrachloride solu- 
tion and set aside to crystallize for 24 hours at the temperature at which 
the solvent was saturated with rotenone. The crystals were filtered and 
weighed in the usual way. 
Seaber (ill) in 1937 reported analyses of derris, barbasco, and 
timbo for rotenone content using carbon tetrachloride, chloroform, 
trichloroethylene, and ethyl acetate as extraction solvents. In the case 
of carbon tetrachloride the srunple was extracted, at least 16 hours, and 
during crystallization the extract was kept at room temperature for 2 days 
and then in ice at least 3 hours before filtering. The chloroform extrac- 
tion method was- essentially that of Beach (3). The error introduced by 
change in volume due to solution of the extract was found to be small and 
was shown to be almost exactly compensated for by the effect of evaporation 
during filtering. Instead of using a mechanical shaker in this method it 
was found that equally good results vv^re obtained by allowing the sample 
to stand in chloroform overnight , shaMng occasionally by hand the next 
day, allowing to stand over another night, and filtering the next day. 
Extraction in a Soxhlet with chloroform v/as tried, but the solvate obtained 
was letss nure . The trichloroethylene method of Cahn and Boam (13) and the 
hot ethyl acetate percolation of Worsley (130.) were also tried. Purity 
of the solvate was calculated by polarization in benzene, which gave re- 
sults a lit tie higher than those by the alcohol-recovery method. 
In almost all cases the chloroform method irave higher results than 
did carbon tetrachloride, and in some cases the differences were large. 
The question as to whether these differences were due to failure of the 
carbon tetrachloride to extract the rotenone or to decomposition was 
studied. In one typical extraction 62 percent of the rotenone was obtained 
in the first 8 hours' extraction with carbon tetrachloride. However, with 
this solvent a limit seemed to be reached before all the rotenone was 
extracted out of the root. Decomposition of rotenone in boiling carbon 
tetrachloride was found to be a factor in lower results by this solvent. 
Boiling rotenone in this solvent for 16 hours gave a loss equivalent to 
about 0.2 percent on a 5-percent rotenone root, and for 72 hours a loss 
equivalent to about 0.5 percent on a similar root. It was stated that 
carbon tetrachloride cannot be relied upon 'to extract rotenone completely. 
Extraction by the ethyl acetate method gave result^ in agreement with those 
by the room-temperature chloroform method but the solvate obtained was less 
p\ire. Seaber recommended as the best method for commercial purposes extrac- 
tion with cold chloroform, crystallization from carbon tetrachloride,' and 
determination of purity by polarization, the result to be reported in terms 
of pure rotenone . 
