- 26 - 
in other methods. The crystals were washed with a cold saturated solution 
of rotenone in carton tetrachloride and allowed to air-dry to constant 
weight. The value for rotenone was calculated from this weight of crude 
solvate . 
Eowaan ( 106 ) in 1936 again warned against the use of Danckwortt's 
(85) pclarimetric method for the determination of rotenone and stated that 
the most reliable procedvire was some modification of the ex tract ion- crj.'stal- 
li7ation method. 
The appearance of microscopic cr7,'-stals of rotenone was descrited 
"by Poezi-ilscot (96) in 1936 as an aid in the identification of this mater- 
ial in analytical work. 
In 1936 government agencies of the Dutch Sast Indies preoared a 
sample of derris root and sent subsacples for analysis to nine labora- 
tories in various parts of the world. In 1937 Koolhaas and J'eijer re- 
ported the results of this investigation. Values for rotenone on a mois- 
ture-free basis were as follows: 
"P.otenone 
Laboratory Percent 
A — United States Department of Agriculture (Jones) 8.1 (pure) 
B — Department of Agriculture, btraits Settlements 
and federated r.alay States (Georgi) 6.6 (p\ire) 
C— Commercial Museum of the Colonial Institute, 
Amsterdam (Howaan) 9.7 (crude) 
D — The Cooper Technical Bureau, London (Csim and Eoam) 7.7 (pure) 
3 — Rothamsted Experimental Station (Tattersf ield and 
Martin) 8.4 (pure) 
F— Seil. Putt, and Rusby, New York (Seil) 7.5 (crude) 
G — Caeser and Lorentz, Kalle-Saale , Germany 12.3 (crude) 
H — Diethelm, Ltd., Singapore 6.3 (crude) 
I — Laboratory for Chemical Research, Buitenzorg, 
Java (Koolhaas and .''eijer) 9.8 (pure) 
See footnote 1, 
