All wools contain a certain amount of animal oil or grease, which permeates every portion of the fleece. The proportion of oil varies with the breed of sheep. A difference in climate and soil materially affects the yield of oil. This is shown by analyses made of different kinds of wool, both foreign and domestic. Spanish wool was found to have but eight per cent. grease; Australian wool fifteen per cent.; while in some fleeces of Pennsylvania wool as high as forty per cent. was obtained. To extract the oil from the wool, a fleece was put in a tall cylinder and naphtha poured on it. The naphtha on being allowed to drain through slowly dissolved out the grease. This naphtha solution was distilled; the naphtha passing off while grease remained--a dark oil having high specific gravity and remaining nearly solid at the ordinary temperature. I am indebted to Mrs. Richards for this method of extracting the oil. The process is quick and inexpensive, and is applicable to the treatment of large quantities of wool.
The object of these experiments was to find the readiest method of separating wool oil into its bases and acids, and further to identify the various fatty acids. A solution of the oil in naphtha was cooled to 15° C. This caused a separation of the oil into two portions: a white solid fat and a fluid dark oil. The first on examination proved to be a mixture of palmitic and stearic acids existing uncombined in the wool oil. The original wool oil was saponified by boiling with alcoholic potash.
The soap formed was separated into two portions by shaking with ether and water. On standing, the solution separated into two layers, the upper or murial solution containing the bases, the lower or aqueous solution containing the acids. This method of separation is very slow. In one case it worked very well, but as a rule appeared to be almost impracticable. Benzol and naphtha were tried, instead of ether, but the results were less satisfactory. On suggestion of Prof. Ordway, potassium chloride was added to the soap solution partially separated by ether and water. This caused an immediate and complete separation. By the use of potassium chloride it was found possible to effect a separation with benzol and water, also with naphtha and water.
Another means of separation was tried by precipitating the calcium salts, from a solution of the potash soap. From the portion of the calcium salts insoluble in alcohol, a fatty acid was obtained with a melting point and composition almost identical with the melting point and composition of palmitic acid. The aqueous portion of the separation effected by water and ether was examined for the fatty acid. The lead salts of the fatty acids were digested with ether, which dissolved out the lead oleate. 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.
The acid obtained from the first fractionation had the melting point at 75°-76°, indicating an acid either in carbon then stearic or palmitic acids.
The acids obtained from the third fractionation had a melting point of 53°-54° C. This acid in composition and general properties was very similar to that obtained by freezing the naphtha solution of the oil, and is probably a mixture of stearic and palmitic acids. These acids, being in combination with the bases of the oil, would be set free only on saponifying the oil and subsequently decomposing with acid.
In conclusion, I should say that but a small proportion of the fatty acids exist in the wool oil uncombined; that the proportion of oleic acid is small, and can only be obtained in an oxidized condition; that the main portion of the fatty acids is composed of stearic and palmitic acids in nearly equal proportions; that the existence of a fatty acid, containing a higher per cent. of carbon than those mentioned, is not fully established.--N.W. Shedd, M.I.T.