Packaging and storage
Preserve in tight containers.
Foreign kernel oils
Shake vigorously 2 mL with a mixture of 1 mL of fuming nitric acid and 1 mL of water for 5 minutes: the mixture is not more than slightly colored.
Cottonseed oil
Mix 5 mL in a test tube with 5 mL of a mixture of equal volumes of amyl alcohol and a 1 in 100 solution of sulfur in carbon disulfide, warm the mixture carefully until the carbon disulfide is expelled, and immerse the test tube to one-third of its length in a boiling, saturated solution of sodium chloride: the mixture develops no reddish color within 2 hours.
Sesame oil
Mix 10 mL with 10 mL of hydrochloric acid, add 0.1 mL of a 1 in 50 solution of furfural in alcohol, and shake the mixture vigorously for 15 seconds: no pink to crimson color appears in the acid layer when separate layers form. Should any color appear in the acid layer, add 10 mL of water, and again shake the mixture vigorously. In the absence of sesame oil the pink color is fugitive.
Mineral oil and foreign fatty oils
Heat 10 mL on a steam bath with 15 mL of 4 N sodium hydroxide and 30 mL of alcohol in a flask that has a small, short-stem funnel inserted in the neck, and occasionally agitate the mixture until it becomes clear. Transfer the solution to a shallow dish, evaporate the alcohol on a steam bath, and mix the residue with 100 mL of water: a clear solution results (
absence of mineral oil). Add an excess of hydrochloric acid to this solution, remove the layer of fatty acids that rises to the surface, wash it with warm water, clarify it by heating on a steam bath, and allow it to cool to 15
without stirring: the fatty acids remain clear for 30 minutes at this temperature (
absence of foreign fatty oils).
Foreign oils
One volume of the mixed fatty acids obtained in the test for
Mineral oil and foreign fatty oils, when mixed with 1 volume of alcohol, yields a clear solution, which at 15
does not deposit any fatty acid or become turbid upon the further addition of 1 volume of alcohol (
absence of olive,
peanut,
or other fixed oils).
Free fatty acids 401
The free fatty acids in 10 g require for neutralization not more than 5.0 mL of 0.10 N sodium hydroxide.