- 14 - 
by distillation with about 25 cc. of isopropyl alcohol. Usually 
three 25-cc. additions of isopropyl alcohol are made before the 
resins are finally brought 'to constant weight by heating the 
tared distillation flask containing them in a vacuum oven at 
80° C. 
Results by this nethod were said to check with those by ether extraction. 
Discussion 
Undoubted!^ the most generally used method for- determining total 
extract of derris and cube roots is extraction with ether. The principal 
(disadvantage in the use of this solvent is the great length of time re- 
quired to obtain complete extraction. As a matter of fact any solvent 
that gives comparable value? ma?^ be used for this purpose. Mei.jer and 
Koolhaas (89), Jones and Sullivan (76), and ethers have pointed out that 
that the amount of total extract obtained with chloroform agrees very 
well with that obtained with ether, and the time required for complete 
extraction is a matter of a few hoiirs instead of days. The use of chloro- 
form for determining total extract woulc' therefore seem to be much pre- 
ferred to the use of ether. Determinations of total extract in the 
laboratories of this rijreau are made with chloroform. 
vJhfort\inately , the use of (decolorizing carbon in the chloroform 
extraction method for rotenone, altloug,! a distinct advantage from the 
standpoint of rotenone determination, prevents the use of another aliquot 
for total extract as sug-'-ested br Jones and Sullivan (76). Graham (46) 
has shown that some of the extract is ac'sorbec' by the carbon. However, 
it should be -oossibl? to devise a scheme in which the sample is extracted 
with chloroform without carbon and filtered as in the older rotenone 
method (72), a suitable aliquot taken for total extract, the remainder 
treated with carbon and filtered, and the proper aliquot taken for rote- 
none determination. A study snould be made, however, to ascertain wiiether 
or not this scheme would involve loss of rotenone due to adsorption by 
the carbon . ■ 
HOTSNOKS 
i'^etnods designed to determine only rotenone are included in tais 
section. Many other methods, particularly colorimetric procedures, have 
been proposed for rotenone, cut when applied to whole derris and cube 
roots or extracts they also determine additional materials. These methods 
are discussed in otier sections of tnis review. 
Geoffrey (29) in 1895 was the first investigator to isolate rote- 
none in a pure condition. Although not quantitative, the method of separa- 
tion is of interest. It involved prolonged extraction of the plant mater- 
ial (cube) with petroleun ether and crystallization of the crude product 
from alcohol. 
4 
The solubility of rotenone in various solvents ( 73, 74 ) is of interest 
in connection with its determination. 
