- .?2 -■ 
writer's v/ork up. tc this, point. On thin assur.pti-on extracts of approxi- 
mately knc'nT^i rotenone contents were prepared from large samples' of roots 
of 4-percent rotenone content or over. The extracts were subjected to a 
preliminary crystallization in the usual way, and the solvate was removed 
hy suction filtration. The filtrate was then made to a definite volume, 
and aliquots were taken of such a si-^ie as to he equivalent to 25 gm. of 
root samples. The amount of rotenOne remaining in each aliquot wa.s 
calculated from known soluhility figures. To the dried aliquots amounts 
of pure rotenone varying from 0.2 to 2.0 gm. were added, each was treated 
with 25 cc. of carbon tatrachloride , and crystallization was carried out 
"by the proposed method. The actual weij^ht of pure rotenone obtained was 
used witnout correcting for solubility in the carbon tetrachloride. 
Hence from the knov.n solubility of rotenone in carbon tetrachloride at 
C^ C, a loss of 0.07 gra. was to be expected. ' The values for rotenone 
present (amount calculated from solubility plus anount added) were plotted 
against the amount lost in crystallisation (amount present minus amount 
actually recovered). In extracts with norrcal proportions of extractives 
other than rotenon? , the Iocs of rotenone in crysoalli-jation wfs great 
when only small amounts v/ere present, but decreased with increasing amounts 
of rotenone until at O.Oo to 1.0 gm. it he came pr^.ctically constant at 
approximately the loss to be expected from the solvent effect of 25 cc. 
of carbon tetrachloride. Similar results wore ohtained with extracts 
of the same roots preriared to hs.ve both a.bnorina-liy 'ligh and abnoi-mally low 
proportions of nonrotenone resins. Alien extra,cts v/ith normal proportions 
of rotenone were allov/ed to crystalline for 48 hours, coirplete crystal- 
lization to a value approximately equal tq the solubility was obtained v*ien 
only ahout 0.6 gm. of rotenone v^as present. 
An extract of a Siir.atra-tyoe derris root was subjected to the same 
preliminary crystallization except that sufficient pure rotenone was added 
to assure quantitative crystallization. The filtrate was treated in the 
same way as described for those of the 4-percent roots. When about 1 gm. 
of rotenone was present, the loss on crystallization was constant and 
approximately equal to the solubility loss; consequently these resins 
are similar to ordinary resins in tneir effect on rotenone crystallization. 
The author therefore believed that the "hidden" rotenone described by 
Cahn and Boam (13) was a result of the retarded crystallization obtained 
with any extract having a low proportion of rotenone to nonrotenone 
resins; the addition of rotenone merely hastened the crystalliaation. 
The accuracy of the Cahn and Boam method, in which 1 f^a. of extract is 
dissolved in only 2 cc. of carbon tetrachloride, was briefly studied and 
appeared to be equal to that of the author's method. 
It v/as concluded that accurate results by the proposed crystalliza- 
tion method were obtained only wnen the rotenone present was equ.ivalent 
to 4 percent of the root, or waen sufficient rotenone was added to bring 
the amount present during crystallization above this value. lor the 
extracts studied the method' gave values which, in view of the precision, 
were not significantly different from the actual rotenone contents. 
Because of tae widely varying composition of different samples of derris 
and cube root, no general estimate was made of tn? accuracy. 
