be placed at the average figure of .917. It sometimes falls as low as .912 and rises as high as .919. It absorbs from 80 to 90 percent of its weight of iodin. In some samples the weight of iodin absorbed is less, falling as low as 77 percent, but this is only in very extraordinary cascs. Occasionally it goes above 90 percent. Probably the number 87 would represent about the mean percentage of iodin absorbed by most edible oils.

Method of Preparation.-The very finest quality of olive oil is that derived from the hand-picked olive. Just as in the preparation of fruits for the market the very best qualities are carefully picked one by one from the tree, so in the preparation of the highest grade of oil the olives are picked one by one, only those of uniform maturity and character being selected. This specially selected fruit is pressed cold, and the first running from this pressure collected separately is designated in English by the term "virgin oil." Virgin olive oil, therefore, ranks the highest in quality. Unfortunately the use of the term for commercial purposes has not been restricted to the quality of oil to which it actually belongs, and at the present time the expression "pure virgin olive oil" which is placed upon the bottles or containers is no guarantee that this quality of oil is found therein. In fact, this expression upon the label has been found in many instances of olive oil highly adulterated and belonging to the cheapest grade. It would be impossible here to enumerate all the different names by which olive oil is found upon the market. The consumer has to depend for protection upon his knowledge of the character of the dealer and hereafter, to a greater extent than ever before, he may be protected by the application of the pure food laws of the various countries.

After the first pressing from which the best oil is secured the resulting pomace is removed from the press, heated or mixed with hot water, and again subjected to a much higher pressure from which a second quantity of oil is secured, still suitable for edible purposes but of a lower quality than that first produced. While the oils which are obtained in this way are used largely for technical purposes such as lubricating, soap making, etc., they are not infrequently employed as edible oils.

In the largest establishments for the preparation of olive oil the kernels are separated from the pulp, but in the smaller works the pulp and kernel are pressed together. Finally the residue from the second pressure may be dried and extracted with bisulfid of carbon or petroleum ether, by which means practically all the residual oil which the cake contains may be secured. Oils extracted in this manner are wholly unfit for edible purposes and are used or should be used solely for technical purposes, among which soap making is perhaps the most important.

Olive-kernel Oil.-An oil is extracted from the kernel of the olive which in some respects of physical and chemical properties resembles olive oil itself. It is usually not considered suitable for edible purposes. Its taste resembles

more that of almond oil than that of olive oil. Some of this oil is doubtless mixed with olive oil when the pulp and kernel of the olive are pressed together, but the quantity thus secured is not very great and does not introduce into the substance anything which gives a specific reaction. It is by no means as high a grade of oil as that expressed from the flesh of the olive alone.

Peanut Oil.-Peanut oil is the refined expressed oil of the peanut, prepared in the manner above described, and is highly valued as a table or salad oil and, unfortunately, is used very often as an adulterant of olive oil, the mixture being sold under the name of the more valuable of its constituents.

Peanut oil contains arachidic acid, which in combination with glycerine forms one of the constituents which serves to distinguish it particularly from other edible oils. There is no other edible oil which contains arachidic acid in sufficient quantities to lead to any mistake concerning its relationship to peanut oil.

Renard's Test for Peanut Oil as Modified by Tolman.-Place 20 grams of oil in an Erlenmeyer flask. Saponify with alcoholic potash, neutralize exactly with dilute acetic acid, using phenolphthalein as indicator, and wash into a 500 c.c. flask containing a boiling mixture of 100 c.c. of water and 120 c.c. of a 20 percent lead acetate solution. Boil for a minute, and then cool the precipitated soap by immersing the flask in water, occasionally giving it a whirling motion to cause the soap to stick to the sides of the flask. After the flask has cooled, the water and excess of lead can be poured off and the soap washed with cold water and with 90 percent (by volume) alcohol. Now add 200 c.c. of ether, cork the flask, and allow to stand for some time until the soap is disintegrated, then heat on the water bath, using a reflux condenser, and boil for about five minutes. In the oils most of the soap will be dissolved, while in lards, which contain so much stearin, part will be left undissolved. Cool the ether solution of soap down to from 15° to 17° C., and let stand until all the insoluble soaps have crystallized out-about twelve hours are required.

Filter and thoroughly wash the precipitate with ether. Save the filtrate for the determination of the iodin number of the liquid fatty acids by the Muter method. The soaps on the filter are washed back into the flask by means of a stream of hot water acidified with hydrochloric acid. Add an excess of dilute hydrochloric acid, partially fill the flask with hot water, and heat until fatty acids form a clear, oily layer. Fill the flask with hot water, allow the fatty acids to harden and separate from the precipitated lead chlorid; wash, drain, repeat washing with hot water, and dissolve the fatty acids in 100 c.c. of boiling 90 percent (by volume) alcohol. Cool down to 15° C., shaking thoroughly to aid crystallization. From 5 to 10 percent of peanut oil can be detected by this method, as it effects a complete separation of the soluble acid from the insoluble, which interferes with the crystallization of the arachidic acid. Filter, wash the precipitate twice with 10 c.c. of 90 percent (by volume) alcohol,

and then with alcohol of 70 percent (by volume). Dissolve off the filter with boiling absolute alcohol, evaporate to dryness in a weighed dish, dry and weigh. Add to this weight 0.0025 gram for each 10 c.c. of 90 percent alcohol used in the crystallization and washing if done at 15° C.; if done at 20°, 0.0045 gram for each 10 c.c. The melting point of arachidic acid obtained in this way is between 71° and 72° C. Twenty times the weight of arachidic acid will give the approximate amount of peanut oil present. No examination for adulterants in olive oil is complete without making the test for peanut oil.

The above process to be of any particular value can only be carried out by an experienced chemist, but the presence of peanut oil may be readily determined by any one who is experienced by following out the above process.

Where only small quantities of peanut oil are concerned, namely, not to exceed five percent, even in the hands of an experienced chemist, the above process may not lead to certain results.

Peanut oil is obtained from the peanut by the ordinary method of hydraulic pressure. The first cold pressing furnishes the oil of finest character for edible purposes. Subsequent pressures or pressure with heat furnish an additional supply or a great quantity of oil but not of the same palatability. Peanut oil is highly prized as a salad oil either alone or mixed with other oil, notably olive oil and sesamé. The oil is purified by a large settle and by filtration and by the processes usually practiced with other oils of vegetable origin. The oil is easily and completely digested and furnishes an abundant source of heat and energy to the system. The number of calories produced by the combustion of one gram of oil, either by ordinary burning or by oxidation in the body is about 9,300.

The cake which is left after the pressing out of the oil is very highly nutritious, containing still considerable quantitics of oil, the whole of the protein matter, and other digestible solids of the nut.

As before stated, it is extensively used as cattle food and as fertilizer. It may also be ground to a meal and used as human food, but furnishes an unbalanced ration in which the protein is far in excess.

Rape Oil (Colza Oil) (Brassica campestris L.).—There are different kinds. of oil which belong to the general class which is known as rape oil or rapeseed oil. The different kinds are derived from different varieties of Brassica campestris. The English names of the three most important varieties are—(1) colza oil, derived from the sceds of Brassica campestris; (2) rape oil, derived from the seeds of Brassica napus L.; (3) rübsen oil, derived from the seeds of Brassica rapa L. The character of the oil also varies according to the manner of its extraction. The first pressings from the cold powdered seeds is of a finer quality for salad purposes than the heavier later pressings from the hot seeds. The oil is also sometimes chilled and the crystallized stearin separated in order to keep it in a liquid state during the winter time, so that the winter and

summer varieties are sometimes recognized in trade. There is, however, no difference in the other characteristics of the oil.

The specific gravity of rape oil at 15.5 degrees C., compared with water at the same temperature, is about .916. The variations from this mean number are not very great. Rapeseed oil absorbs almost its exact weight of iodin,the average iodin number being not far from 99.

The Chief Adulterations of Rape Oil-The chief adulteration of rape oil consists in the admixture of cheaper or flavoring oils. Among those which are often used in the adulteration of rape oil are linseed oil, hempseed oil, poppyseed oil, chamomile oil, cottonseed oil, the various mustard oils, refined fish and blubber oils, rosin oil, and paraffin. Some of these adulterations, it is seen, cannot be added to rapeseed oil when used for edible purposes. The chief adulteration of rapeseed oil, when intended for edible purposes, is the addition of cottonseed oil. The detection of these various adulterations, with the exception of that of cottonseed oil, can be accomplished only by an expert chemist. The presence of cottonseed oil can be detected by the application of the Halphen test already described.

Technique of Extraction.-The extraction of oil from the rape seed is not different from that of other oily seeds. It is either extracted by pressure, which is the proper way always when it is to be used for edible purposes, or when used for technical purposes it may be extracted by means of carbon bisulfid or petroleum ether. When extracted by pressure for edible purposes the oil should be refined by a similar treatment to that applied to cottonseed oil and finally filtered, preferably after mixing with fuller's earth or other similar material, in order that it may be perfectly pure and bright and free from suspended matter which interferes with its utility as an edible oil.

A very common treatment of the expressed oil, in order to coagulate and separate the mucilaginous matter which it contains, is with sulfuric acid. This acid has the very valuable property of coagulating this class of bodies. When treated with sulfuric acid it is necessary that the oil be thoroughly washed many times in pure water in order to remove the last trace of the acid. The residue or oil cake is prized as a cattle food or as a fertilizer. average content of oil in rape seed is about 37 percent.

The

Sesame Oil.-Sesamé oil is very commonly used for salad oil and for the other purposes to which the edible oils are devoted. It is also known as gingili oil and teel oil. Sesamé oil is obtained by pressure from the seed of the sesame plant, Sesamum orientale L.

Sesamé oil possesses a light amber color when properly made, is free from any unpleasant odor, has an agreeable taste, and when expressed cold produces what is known as the cold-drawn oil which is regarded by many as of equal palatable value with olive oil. Sesamé oil, in addition to containing stearin, palmitin, and olein, also contains a small quantity of a glycerid which exists in large quantities

in flaxseed oil, namely, linolein. When prepared for edible purposes it contains only a small quantity of free acid, is free from rancidity, clear, and brilliant in appearance and has a sweet agreeable taste. The specific gravity of sesamé oil at 15 degrees C. varies from .9225 to .9237. It absorbs from 103 to 108 percent of its weight of iodin and has a refractive index at 15 degrees of about 1.4748.

Adulteration of Sesamé Oil.-Some of the other vegetable oils are cheaper than sesamé and are added to it for the purpose of adulteration and cheapening the product. Among the most common oils used for the adulteration of sesamé are poppyseed oil, cottonseed oil, and rape oil. The presence of cottonseed oil in sesame oil is easily distinguished by the Halphen test already given. The presence of poppyseed oil is revealed by the high iodin number and the high degree of heat produced when mixed with sulfuric acid.

Only the best variety of cold-drawn sesamé oil is used for edible purposes and for making oleomargarine. The inferior qualities are used in soap making, the making of perfumes, etc., and the lowest quality of oil is used for burning purposes.

Characteristic Reaction.-A test which is known as Baudouin's is extremely delicate and reliable and is easily applied. It consists in the development of a red color when a small quantity of sesamé oil is treated with hydrochloric acid in the presence of furfural. The test is easily carried out as follows: Place a few drops of a two percent solution of furfural in a test-tube with 10 cubic centimeters of sesamé oil or the oil to be tested for sesamé and 10 cubic centimeters of hydrochloric acid of 1.19 specific gravity, and shake the mixture well for half a minute. When the tube is left at rest, if sesamé oil be present the aqueous acid layer which forms will have a distinct crimson color. Any coloration which is produced by other oils is entirely distinct from this one and therefore can be easily distinguished.

Geographical Distribution. The sesamé plant is grown chiefly for commercial purposes in India, China, Japan, and West Africa. The technical preparation of the oil, in so far as is known, is not practiced in the United States. It is pressed and prepared for commerce chiefly in France. The seeds are rich in oil, yielding a larger percentage by pressure or extraction than most of the oil-bearing seeds.

Sunflower Oil.-The oil extracted from the seed of the sunflower is of high quality for edible purposes. Although not in general use in this country, it is very extensively used in Russia and some other parts of Europe. There is every reason to believe that a profitable industry could be established in the preparation of edible oils from sunflower seeds. The plant grows in the greatest luxuriance in nearly all parts of the country, and the yield is sufficiently great to make it an object of more interest to our agricultural population than it is at the present time.