Chemical examination of watermelon seed / by Frederick H. Power and Arthur H. Salway.

  • Frederick Belding Power
Date:
[1910?]
Catalogue details

Licence: In copyright

Credit: Chemical examination of watermelon seed / by Frederick H. Power and Arthur H. Salway. Source: Wellcome Collection.

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    extracted successively in a Soxhlet apparatus with various solvents. The results were as follows: Petroleum (b. p. 30-45°) extracted 25.6 grams = 38.8 per cent. Ether U 3-2 a = 4-8 U Chloroform u 9.2 « = 13-9 u Ethyl acetate a 3-4 U = 5-2 a Alcohol u 7-4 u = 11.2 u Total, 48.8 a = 73-9 u Petroleum Extract of the Resin. This extract was a dark, viscid liquid. On the addition of ether a small quantity of a gelatinous substance separated, which was removed by filtration. This substance was very sparingly soluble in alcohol, but readily soluble in hot acetic acid, and also in pyridine, from both of which solvents it was again deposited in a gelatinous form. The portion of the extract which was soluble in ether was heated with an alcoholic solution of potassium hydroxide. After removing the alco¬ hol, water was added and the alkaline liquid extracted with ether. The ethereal liquid, after the removal of the solvent, yielded about 0.5 gram of a light yellow solid, which, when crystallized from a mixture of ethyl acetate and alcohol, separated in glistening leaflets, melting at 138-140°. The melting point and color reactions of this substance indicated that it was identical with the phytosterol, C20H34O (m. p. 141-142°), obtained from the fatty oil of the shells of watermelon seeds. The alkaline solution of potassium salts, after extraction wflth ether, was acidified with sulphuric acid and again treated with ether, the ethereal liquid being washed, dried and the solvent removed. The fatty acids thus obtained were distilled under diminished pressure, when the greater portion passed over between 235 and 240°/20 mm., a small fraction having also been collected at 240-260°/20 mm. The fraction 235-240°/20 mm. became partially solid on cooling. The solid portion was therefore removed and crystallized from alcohol, when, after the first crystalliza¬ tion, it melted at 55-58°. 0.3334 neutralized 12.05 cc. 0.1 N KOH. Neutralization value = 202.8. C18H3602 requires a neutralization value of 197.5. CleH3202 requires a neutralization value of 219.1. It was thus evident that the above portion of solid acid consisted of a mixture of palmitic and stearic acids, the former predominating. The liquid portion of fatty acids from the fraction 235-240°/20 mm., when tested with nitric acid, was found to contain some oleic acid. 0.2331 absorbed 0.3301 iodine. Iodine value = 141.6. These liquid fatty acids, therefore, like those contained in the expressed oil of watermelon seeds, evidently consisted of a mixture of oleic and linoleic acids.
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