- 43 - 
purity of the complex was ca^^ried out by a polarimetric method. The optical 
rotation of a 4-percfcnt roluticn cf the solvate in "ben'rene was determined, 
and the percentage of rot3non^ tnen calculated from the rotation of pure 
carbon tetrachloride solvate in ben'^ene. It v,as stated that impurities 
present were likely to rhov/ a specific rotation ap-pro'cimately one-fourth 
that of rotenons. x]-.3 error involved v/as said to be small but mi,5;ht be 
allov/ed for if it was ccnsicieiGd necessary. Valiies obtained cy this method, 
in general, agreed with t'lops cbtai.ied by the dichloroc-icatic acid titration 
method (67). 
The Imperisl Ins^ibnte (57), in a surv.^y of insecticides from plant 
materials in 1940, oriefly discussed the evc.luatio-i of derrls and cube. 
It was stated that results for rctenone depend.ed on the solvent, the number 
of extractions, tha tempe'^ature and leijf:th of time of extraction, as v/ell 
as on the finenerss of gri-iding and moist'ore content of the sEjnple . The 
need of a standardised method v/as stressed. 
In the Official and Tentative I.:Hhcds of Analysis. of th3 Association 
of Official AfiTiculo\iral Chemists (Z) ^re f cllov/in^'; method for determining 
rotenone, that recornisnded ^y Graham (ji?) , i^ girexi as "official, first 
action": 
"weigh 30 g. (if samplo contc.ins inors than 7,^ rctenone 
use a quejitity that v/ill give 1.0 - 1.5 p. of rctenone in the 
200 ml. aliquot) of finely powdered rco-b aiid 10 g. of decolor- 
izing carbon into 500 -nl. glass-stoppersd lirlerjneyer flask. 
Add 300 r.l. of cnlor->form neesurod at definit-=! roca temperature; 
place' flask on shakir.g machine and fasten stopper secure].?/. 
Agitate vi;3orously for not less th^n fo-jr ho-ars, preferably 
interrupting shaking v;ith overnight re«t (or flask iosy be shaken 
continuoi''sly overni,5^t). P-Sinove flask irom machine end alJ.ov; 
to cool in refrigerator for at least an hour. Filter mixture 
rapidly into suitable flask, usiiifj fluted paper without suction 
and keeping funnel covered with watch glass to avoid loss from 
evaporation, titoppor flask and adjust temperature cf filtrate to 
that of original chloroform. 
"Transfer exact?.y 200 ml. o^? this solution to 500 n.l. Pyrex 
3rlenmeyer flask and distil until only about 25 ml. regains in 
flask. Transfer extract to 125 ml. 3rlenme:'-er flask, ■'.ising 
carbon tetrachloride to rinse out the 500 ml. flask. Svaporate 
almost to dr7,rress on stea'a bath in current cf air. Then remove 
remainder of solvent uiider reduced pressure, heating cautiously 
on ste-Mf; bath when necessary to hasten evaporation (suction may be 
applied directly to flask). Dissolve extrs-ct in 15 ml. of hot 
carbon tetrachloride and again, in a similar manner, remove all 
solvent. Repeat with .another 10 - 15 ml. portion of hot carbon 
tetrachloride. (This treatment removes all chloroform from the 
resins. The chloroform extract is visually completely soluble in 
carbon tetrachloride. If small quantities of insoluble material 
are present, the purification procedure doscribod later will 
eliminate them. However, if large qua.ntity of insoluble residue 
should remain when -extract is dissolved in first portion of 
carbon tetrachloride, it should be filtered off and thoroioghly 
