2 BULLETIN 8%, U. 8. DEPARTMENT OF AGRICULTURE 
the name of pyrethrotoxic acid, and Fujitani, who claimed that it is a 
neutral ester, which he named pyrethron. 
Work DoneE FRom 19238 To 19248 
In 1923 work on Pyrethrum was resumed with the object of 
isolating the active principle in pure condition. About 2 kilos of a 
coarse powder ground from whole Dalmatian flowers was extracted 
in a glass percolator, using petroleum ether boiling between 20° and 
45° C. as the solvent. Decidedly less extracted material was ob- 
tained when light petroleum-ether was used (about 1.8 to 2.5 per 
cent). The oily product obtained by evaporating off the solvent 
was poured into a large volume of 95 per cent alcohol, which caused 
the precipitation of a waxy material. The alcoholic solution was 
allowed to stand in the cold room at a temperature of about —5° C. 
for 24 hours, which caused the separation of more fats and waxes. 
The solution was filtered in the cold and the alcohol evaporated in 
vacuum. The resulting thick sirup was subjected to distillation in 
a vacuum of 1 to 2 millimeters, using small quantities of material for 
each distillation. Foaming caused some trouble, but careful opera- 
tion made it possible to distil over about 20 per cent of the material. 
The distillate was collected between 100° and 190° C. The tem- 
perature of the oil bath ranged from 140° to 230° C. The distillate 
was a light yellow oil, which partly solidified on cooling to a mass of 
about the consistency of butter. 
By direct saponification of this crude distillate with alcholic potash, 
the pyrethronic acid of Yamamoto (S32) was obtained and converted 
into the dihydroxy acid, which was recrystallized from a mixture of 
acetic ether and petroleum ether. It melted at 146°-147° C., and 
the analytical results agreed with those reported by Yamamoto. 
In order to remove the free acids, the crude distillate was dissolved 
in alcohol and treated with a solution of lead acetate. This gave the 
lead salt of an acid, from which the free acid was isolated and purified 
by recrystallization from alcohol. It was identified as palmitic acid. 
The alcoholic solution was evaporated, the residue taken up in 
ether and extracted with water, and the solvent evaporated. In 
later experiments the first distillates were dissolved in ether and 
extracted with dilute alkali and the ethereal solutions were dried with 
sodium sulphate. The residue from the ethereal solution was sub- 
jected to repeated fractionation in a vaccum of about 2 millimeters. 
The material distilling up to 150° C. was discarded and the main 
portion of the distillate boiling between 150° and 166° was collected 
separately and again distilled. The product boiling between 153° 
and 166° was analyzed, with the following results: Carbon, 74.20 
pe cent; hydrogen, 9.26 per cent; molecular weight, 293 by the 
reezing method; density at 20° C., —12.84°. Several preparations 
obtained by this method and analyzed showed only slight deviations 
from the values given. From the analytical figures the formula 
C,sH,,O0, was calculated. Determinations of the molecular weight 
by saponification, however, showed a slightly higher value than that 
found by the freezing point method, indicating the presence of 5 
to 10 per cent of unsaponifiable material. Different preparations 
and different fractions of the same preparation taken at only slightly 
different temperatures also showed varying refractive index values. 
8 Conducted by F. B. LaForge. 
