- 7^7 - 
wate-r. The crystals are then dissolved in chloroform', atout 50 cc. 
.of vater is added, and the. mixture titrated with O.I.N alkali usinf 
phsnolphthaloin ?"-s inc'lcat-or . 
With proper care in th? acicUtion of v/ater during the precipitation, 
the acid solvate separated in a crystalline form from which excess acid 
was readily washed. In tests on specially prepared cart.cn tetrachloride 
solvates, the method ^ave values for purity about 2 percent higher than 
those "by the older alcohol-recovery test. Results on samples of pov/dered 
root were in good agreement with those by the older ^avimetric procedure. 
The procedure effected a saving in time over the .-Tavimetric method and 
neutral impurities, such as sulfur, did not interfere. Attempts to pre- 
cipitate the acid solvate directly from whole derris and cubs extracts 
in an effort to shorten th-^ procodure still further met v;ith failure. 
In his 1938 report to th--- Ass<^ciation of Cfficia.l Agricult-or-al 
Chemists, Graham (47) r?v? the results of a collaborati''-e study comparing 
the crystalli?:3tion method of Jones and G-rah.am (72) with the titration 
method (S7). The former method .frave good results on both derris and cube, 
but several collaborators had difficulty with the latter procedure. 
At the 1933 meeting of the ilational Association of Insecticide and 
disinfectant i-anufact"'arers, Graham (45) reviev/ed methods of analysis for 
rotenone. Extraction of the sample with carbon tetrachloride in a Soxhlet, 
although widely used, was said to have several disadvantages, amon^r which 
were difficulty in obtaining complete extraction and decomposition of the 
solvent due to moisture present, with consequent decomposition of the 
rotenone. Chloroform extraction at room temperature was recommended. 
It v/as stated that a modification of the crystallization method na,d been 
developed for the dete^rmination of rotenone in the presence of sulfur. 
The method was not described, but it ivas said thjat the rotenone a,nd con- 
taminating sulfur v/ere weighed and a correction was then made for the amount 
of sulfur present. Tae- titration method v/as also said to be applicable 
to such mixtui-es. 
Details of th? rr.-^tho'' used in the pr-^sence of sulfur have been 
furnished by the Agricultural Marketing Se'-vice ( 126 ) . Extraction v/as 
carri<?d out in the usual way and the evaporated extract was then treated 
as follows: 
"Add 30 cc. of acetone to the residue, v.'arm to dissolve 
the rotenone, cool in running tap water for 15 m.inutes, filter 
through a disc of filter paper in a Gooch crucible and wash 2 
or 3 tines with 10 cc. portions of acetone. Transfer the 
acetone solution to a 125 cc. Erlsnmeyer flask an J evaporate 
almost to drjTiess on a steam bath in a. current of air. Then 
completely remove the remainder cf the solvent under reduced 
pressure," 
The remainder of the 'or.ocediire w.a.s the same as that usually efrploysd , 
beginning with the addition of carbon tetrachloride. 
