- 44 - 
washed with further portions of hot solvent, aftsr v/hich the 
filtered solution plus washings should oe treated as directed 
above for removal of chloroform.) 
"Add exactly 25 rl . of carhon tetrachloride and heat gently 
to completely dissolve extract. Cool flask in ice bath for several 
minutes and seed with a. fev; crystals of rotenone-carbon tetra- 
chloride solvate if necessary. Stop-oer flask and sv/irl until crystal- 
lization is apparent. If at this stage only a small q^iantity of • 
crystalline material separates, add an accurately weighed quantity 
of pure rotenone estimsted to be sufficient to assui'e that final 
result, expressed as pure rotenone, is at least 1 g. Then warm to 
effect complete solution, and again induce crystallisation. At same 
time prepare a saturated solution of rotenone in carbon tetra- 
chloi^dB for washing. Place flasks containing extract and v/ashins 
solution in ice bath capa.ble of maintaining temperature of 0° G. 
and allow to remain overnight. 
"After 17-18 hours in ice bath, rapidly filter extract 
through weighed Gooch crucible fitted with disc of filter paper, 
reproving flask from ice bath only long enough to poiu" each frac- 
tion of extract into crucible. Hinse residue of crystalline 
material fvoir, flask and wash under suction vrith sufficient of ice- 
cold saturated solution (usually 10 - 12 ml.) to remove excess 
mother liquor. Allow crucible to remain under suction for about 
5 minutes and then dry to constant weight at 40° C. (about an hour). 
The weight obtained is 'crude rotenone-carbon tetrachloride solvate'. 
"Break up contents of crucible with spatula, mix thoroughly, 
and weigh 1 g, into 50 ml. -^rlenmeyer flask. Add 10 ml. of alcohol 
that has previously been saturated with rotenone at room tempera- 
ture, swirl flask a few ninutes, stopper tightly, ajid set 
aside at least four hours, prefer-^bly overnight, at the same 
temperature. J'ilter on v/eighed C-ooch crucible fitted v/ith disc 
of filter paper. P-inse crystals from flask and wash under suction 
with solution of ethyl alcohol saturated with rotenone at tempera- 
ture of recrystalli^ation lea. 10 mi will usually be required). 
Allow crucible to rer:vain ur-der suction 3 to 5 ninutes and then dry at 
105° G. to constant weight, which should be effected in 1 hour. 
""'ultiply weight expressed in gra:nnn b^- v;5ight of the 'crude 
rotenone-carbon tetrachloride solvate' and to prodi\ct add 0.07 g. 
which represent b correction for rotenone held in solution in the 
25 ml. of carbon tetrachloride used in crystallization. If any pure 
rotenone has been add.ed, subtr.-^ct its weight from vilue obtained. 
This gives the weight of pure rotenone contained in bhe aliquot of 
the extract, representing 20 grams of the sample. 
"Alternate extraction procedure. - If sample is one in which 
ratio of rotenone to total extract is greater than 40/j, use quantity 
sufficient to contain 1.0 - 1.5 g. of rotenone and successively 
extract four times with CHGlr^, using 200 ml. each for second to 
fourth extractions, filter after each extraction and return marc 
