54 
Gravimetric Methods 
T^ucei, MiyaJiTia, ard Ono ( 118) in 1933 developed a gravimetric method fOr 
detemining rotenone anddeguelin. This nethod, which has been "briefly discussed 
under Hctenone, is "based on the fact that rotenone and deg^aelin are readily 
oxidi:2ed under alkaline conditions to rotenolones and degaelinols, respectively, 
vhich are quantitatively dehydrated by alcoholic sulfuric acid to the hi,^hly in- 
soluble dehydrorot-enone and dohydrode^uelin.- r.ie mixture of d^hydro coiapounds 
gives a value for total rotenone plus deg-aelin. A value for dc^elin alone 
Was obtained by subjecting the dehydro co^rjounds to aporopriate cat-Jytic 
hydro genat ion, vhich con-'-erted the dehydro rotenone to the alkali-soluble 
isodinydrodehydro rotenone (dehydrorotenonic acid) while the dehydrodeg-ielin 
reraintd unchanged. In the original r.ethod much of the rotenone was first 
cr:,"stallized out. Die nethod is briefly as follo^^'s: 
The rotenone is first cr-'stellized fron an ether ertract in 
the uoual v.^ay. live grar,s of th?- evaporated mother liquor is 
dissolved in 150- cc. of alcohol and 3 gm. of S-^Dercent alcoholic 
sodium hydroxide is adaed. 0:cygen is passed in at the rate of 
150 cc. per minute for l/S hour. If air is used instead of ox^rgen, 
it is run through for 1 1,/?, to 2 hours. The reaction product is 
acidified vith 15 grn. of 50 — ercent alcoholic sulfuric acid, and 
130 cc. of alcohol is distilled off on the ^^rater bath during 1/2 
hour. The residue is refluxed another hour. It is nixed with 
500 cc. of water and shak-r-n vj _^orour!ly v/ith SCO cc. of ether in a 
separetory funnel. The dehydro ceriv -tives are suspended in the 
ether layer, other materials dissolve in either thr water or the 
ethor layer. The entire mixture is filtered by suction, and the 
crystals are washed with 10 cc. of methyl alcohol. The yellow* 
needle crystals a.r9 dried at 100° and weighed. ' This value gives 
the weight of any rotenone not separated in the original ether 
crystallization plus the deguelin. A small quantity of crystals 
may also be obtained from the filtrate. Five-tenths ^.rsia of the 
mixture of dehydro compo-ands and 0,5 gn. of palladium-bariuT. sulfate 
catalyst are placed in 100 cc . of alcohol and mixed witri 3 c6, of 
3-percent sodium hydroxide. The mixture is shaken in an atmosphere 
of hydrogen for 2 hours, and then filtered. The residue consists 
of dehydrodeguelin and catalyst, it is extracted vdth acetone, ajid 
evaporation of the extract gives the dehydrodeg'j^elin. Most of tne 
alcohol is distilled from the filtrate, vhich is then acidified 
with sulfuric acid and extracted with ether. Zvapor.ition of the 
ether extract gives the isodihydrodehydrorotenone. 
Danc':vortt, Buido, and Ba-'angarten {2Ji) in 1934 stated that the foregoing 
method might be theoretically unobjectionable but it was very trouolesor.e and 
time-consuming and required a la.Tr;e amount of aoparatus. 
Fischer and "itsche (?8) strted that the method was too bothf^rscme and 
time-consuming in its complete execution. They found it useful, howev r, for 
determining only the rum of rotenone and deguelin. Essentially the directions 
of Taicai ft fT> were used, but in v;ashing the sepi^.rated dehydro compounds the 
methyl alcohol w-^sh was follow<:.d with a small amount of ether. IVequently a 
