DETERMINATION OF UNSAPONIFIABLE MATTER.
In order to determine the unsaponifiable matter in fats and oils they are first saponified, then the unsaponifiable, which consists mainly of hydrocarbons and the higher alcohols cholesterol or phytosterol, is extracted with ether or petroleum ether, the ether evaporated and the residue weighed as unsaponifiable.
To carry out the process first saponify about 5 grams of fat or oil with an excess of alcoholic potassium hydrate, 20-30 cubic centimeters of a 1 to 10 solution of potassium hydroxide in alcohol until the alcohol is evaporated over a steam bath. Wash the soap thus formed into a separatory funnel of 200 cubic centimeters capacity with 80-100 cubic centimeters water. Then add about 60 cubic centimeters of ether, petroleum ether or 86 degs. gasoline and thoroughly shake the funnel to extract the unsaponifiable. Should the two layers not separate readily, add a few cubic centimeters of alcohol, which will readily cause them to separate. Draw off the watery solution from beneath and wash the ether with water containing a few drops of sodium hydrate and run to another dish. Pour the watery solution into the funnel again and repeat the extraction once or twice more or until the ether shows no discoloration. Combine the ether extractions into the funnel and wash with water until no alkaline reaction is obtained from the wash water. Run the ether extract to a weighed dish, evaporate and dry rapidly in a drying oven. As some of the hydrocarbons are readily volatile at 100 degs. Centigrade, the drying should not be carried on any longer than necessary. The residue is then weighed and the original weight of fat taken divided into the weight of the residue × 100 gives the percentage unsaponifiable.