F. A. Csonka 405 
At the end of the titration of the fatty acids by the method of Gephart 
and Csonka!! the fatty acids are present as potassium soaps in a mixture of 
petroleum ether and alcohol. <A portion of the blood cholesterol is present 
in this same solution. To remove the cholesterol the solution is made 
alkaline, to insure separation more alcohol is added, and extracted twice 
with petroleum ether. The alkaline solution containing the fatty acids 
as soaps is transferred to a large beaker, evaporated on the water bath, 
the residue dissolved in warm distilled water, neutralized by acetic acid, 
and the fatty acids are precipitated as lead soaps by the addition of an 
excess of lead acetate solution. The soaps are then filtered off and dried 
in vacuum. The ether-soluble lead soaps are decomposed by the addition 
of hydrochloric acid; the free unsaturated fatty acids, after the ether is 
distilled off, are dried in vacuum, weighed, and saved for the determina- 
tion of the iodine number according to Hiibl. 
Since the iodine number of the unsaturated fatty acids in sev- 
eral cases as shown in Table I is higher than that of oleic acid, the © 
TABLE II. 
CORB NG Og Fg ap) a0 oid k'> S's Venn sits 3 9 10 14 18 19 
MIRC POs ie Life shnns Cts arena acon oe by pistes 117.2 101.1 129.6 136.9 96.4 108.6 
Unsaturated fatty acids of alco- 
hol-soluble barium soaps, gm. 
Ine L00- cer Of Dlood <5 60. see 0.035} 0.1386) 0.054} 0.165) 0.075} 0.084 
question of the direct evidence of the presence of other or higher 
unsaturated fatty acids arose in the latter part of this work. 
Therefore, the unsaturated fatty acids were dissolved in abso- 
lute alcohol neutralized by alcoholic KOH and the oleic acid was 
partly precipitated as barium oleate, placed in a refrigerator for 
a few hours, and then filtered. The unsaturated fatty acids of 
the alcohol-soluble barium soaps (Table II) were liberated by 
hydrochloric acid, extracted by ether, and after the ether was 
evaporated off the residue was dried, weighed, and used for the 
determination of the iodine number. 
I was especially careful to avoid any alteration or destruction 
of the unsaturated fatty acids which may result from the use of 
excessive heat. The saponification and extraction flask described 
in the previous communication? was used to advantage in this 
work. 
THE JOURNAL OF BIOLOGICAL CHEMISTRY, VOL. XXXIII, NO.3 
