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._
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