- 25 - 
carbon tetrachloride satiorated with rotenone for every cram of' 
r=»slns plus rctenone is added, and the mixture is warmed until 
solution is complete. The beaker is set aside until morning ' 
in a desiccator containing a dish of carbon tetrachloride; 
seeding is unnecessary. The crystals sre filtered through a 
Gooch crucible on a disk of filter paper. They are washed 
with solvent (carbon tetrachloride-rotenone) until no further 
color is removed and dried for about 6 nours at about 40^^ C. 
The weight obtained tiacc 0.719 gives the amo-ont of crude 
rotenone. 
The purity is most accurately doterminsd by triturating 
the rotenone-carbon tetrachloride complex with absolute alcohol 
saturated v/itn rotenone, 5 cc. for every grrjn of complex, and 
leaving overnignt in a c'.esiccatcr containing a cish oi alcohol. 
The rotenone is collected iu a Gooch crucible, washed with 30 
to 40 cc. of the solvent, and dried at 100° for 6 hours. Frpm 
the wei£:nt of rotenone thus obtained the amount originally 
added is deducted; tie difference is the amount in the sample. 
The purity of this rotenone may be deterrnined by weighing out 
between 0.48 and 0.50 gm., dissolving in a stoppered vessel in 
10.00 cc. of pure benzene, and ceteri^iining the angle of rota- 
tion in a 200-mm. tube. From a previously prepared curve, or 
from the formula C = (alpha - i.428)/4.066, tne concentration of 
pure rotenone is obtained and the purity thus determined. The . 
purity ma^/ be taken as bein^; 95.2 Toercent, and this means tiiat 
for rotenone contents above 6 percent a correction of -0.1 percent 
is made, but for contents below 6 percent no correction is necessary. 
A less accurate result for pure rotenone can be obtained by 
determining the angle of rotation of the rotenone-carbon tetrach- 
loride complex by weit;hing out betv/eeh 5.8 and 7.2 gm. arid dissolv- 
ing in 10.00 cc. of pure benzene. As before, tne concentration 
of pure rotenone is determined and the percentage purity of rotenone 
in the "complex calculated; from this figure 2.6 is deducted and the 
difference used to calculate pure rotenone in the sample. 
An even more rapid method is to assume taa purity of the comr- 
plex to be 94 percent and to calculate r)ure rotenone on this basis. 
Sxcept for a few unusual derris samples results of sufficient 
accuracy for routine estimations are obtained. 
In 1936 many comiaercial analysts of derris and cube roots were using 
a method for rotenone developed by H. A. Seil.^ This method has not been 
publisned, and several variations have been brought to the attention of 
the reviewer. In this method 50 gm. of root was extracted with carbon 
tetrachloride in a Soxhlet for 5 to 7 hours, or longer if necessary. Before 
extraction 0.34 gm. of rotenone-carbon tetracnloride solvate v/as added to 
the extraction flask, and after extraction the extract v/as concentrated to 
40 cc. Crystallization and filtration of the solvate were carried out as 
c 
Details of this method were obtained in 1936 in private communications 
from licCormick pjad Co. and John Powell and Co. 
