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It depends upon the principle that when acetic acid is poured drop by drop into an alcoholic solution of oleic acid, there comes a time when all the oleic acid separates, but stearic acid, which is insoluble in a mixture of alcohol and acetic acid, remains insoluble if the mixture contains oleic acid.
The root, which is the saponaceous portion of the plant, resembles the onion, but possesses the quality of cleansing linen equal to any "oleic soap" manufactured by my friends Cornwall and Brother, of Louisville, Ky.
By pressure the fluids are mixed and the pores are closed. A stuffing box filled with this mixture has worked three years without grinding the piston-rod. In the same manner I close the screw-thread hole in gas tubes used for conducting steam. When the tube is screwed in the socket, the powder mixes with the oleic acid. The water coming in at first makes the linseed powder viscid.
From this oleic acid was obtained. This was further purified by forming the Boreum salt of oleic acid. The lead salts not soluble in ether were decomposed by acid. The fatty acids set free were saponified by carbonate of potassium. A fractional precipitation was effected by adding lead acetate in successive portions; each portion sufficient to precipitate one-fourth of all the acids present.
But since cotton seed oil, for example, which is most frequently used to adulterate olive oil, contains 5 per cent. of glycerine, and 59.5 per cent. of oleic acid, it is easy to see an admixture of cotton seed oil cannot be detected by this method, which appeared to be so exact.
You now see, no doubt, the necessity of sharply discriminating between two classes of colouring matters, which we may term colour acids and colour bases respectively. There are but few acids that act like tannic acid in fixing basic aniline dyestuffs, but oleic acid and other fatty acids are of the number.
With a glass rod place a drop or two of strong nitric acid containing nitrous acid near the drop of bile; bring the acid and bile into contact. Notice the succession of colors, beginning with green and passing into blue, red, and yellow. Experiment 79. To show the action of bile on fats. Mix three teaspoonfuls of bile with one-half a teaspoonful of almond oil, to which some oleic acid is added.
The conversion into soap is a very simple matter. As the fats are acids a mixture of palmitic, oleic, and stearic acids and not the glycerine salts of these acids, like ordinary fats, soap is made by causing them directly to unite with caustic soda.
This amount of pure oleic acid would require 33.95 c.c.; of pure stearic acid, which has almost the same molecular weight as oleic acid, 33.71 c.c.; or of pure palmitic acid, 37.4 c.c. This, taken in conjunction with the way in which the acid melted, makes it extremely probable that it is a mixture of oleic and stearic acids.
This acid was proved to be oleic, by its saturating power and its melting point, which were fairly concordant with those of the pure acid. Appearance, etc. The sample was of a deep brown color, of a fluidity intermediate between olive and castor oil, and possessed a strong, rather disagreeable odor. The Specific Gravity at 60° Fahr., 914.0.
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