8 BULLETIN 1057, U. S. DEPARTMENT OF AGRICULTURE. 
The acid present in the largest proportion possesses the formula 
C 18 H 32 2 , and has been designated chaulmoogric acid, with reference 
to the vernacular name of the oil. It is accompanied by a lower homo- 
logue, C 16 H 28 2 , which has been termed " hydnocarpic acid," on ac- 
count of having first been isolated from a Hydnocarpus oil. Both of 
these acids are beautifully crystalline substances, from which a num- 
ber of derivatives have been prepared, and their constitution has also 
been definitely established. They constitute what is now known as the 
chaulmoogric acid series. 
Chaulmoogric acid, C 18 H 32 2 , melts at 68.5° C. and is dextrorota- 
tory, having [<z]d + 62.1°. Although isomeric with linolic acid, it 
is capable of combining directly with only two atomic proportions of 
bromin or iodin. It must, therefore, possess only one ethylenic 
linking and contain in its structure a closed carbon ring, which has 
been shown to be the case. The methyl ester (methyl chaulmoograte) 
distils at 227° C. under a pressure of 20 mm. as a colorless oil, which 
on cooling forms a solid mass of needles, melting at 22° C. The 
ethyl ester (ethyl chaulmoograte) is a colorless oil, which boils at 
230° C. under a pressure of 20 mm. 
Hydnocarpic acid, C 16 H 28 2 , melts at 60° C. and like chaul- 
moogric acid is optically active, having [<z]d -j- 68°. Its methyl 
ester is a colorless oil, which boils at 200° to 203° C. under a pres- 
sure of 19 mm. When cooled it solidifies to a mass of colorless crys- 
tals, which melt at 8° C. The ethyl ester is a colorless oil, which 
boils at 211° C. under 19 mm. pressure. 
Besides the above-mentioned acids, chaulmoogra oil contains a 
small amount of palmitic acid, together with an acid or acids hav- 
ing a higher iodin value than either chaulmoogric or hydnocarpic 
acid. As was noted several years ago, this observation, in connec- 
tion with other characters of the acids, indicated the presence in the 
oil of an acid or acids of the series C n H 2W _ 4 2 , but with two ethylenic 
linkings. Inasmuch as linolic acid, C 18 H 32 2 , possesses two ethylenic 
linkings and an iodin value of 181.2, it is probable that a considerable 
proportion of this acid is contained in both chaulmoogra and hydno- 
carpus oils. Linolenic acid, C 18 H 30 O 2 , which contains three ethylenic 
linkings and has an iodin value of 273.7, may also be present. 
An interesting occurrence of chaulmoogric acid has been recorded 
by Goulding and Akers (8, 10) . They obtained it from the fatty oil of 
so-called " Gorli " seed from Sierra Leone and found it to be present 
to the extent of 84.5 per cent in the mixed acids, the remainder con- 
sisting of liquid acids having a higher iodin value and therefore 
more unsaturated. The botanical source of these seeds is Oncoba 
echinata Oliver, which belongs to the same family as the chaulmoogra 
tree. 
