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To Restore Rancid Fat or Oil

Another method is to thoroughly wash them with hot water, frequently renewed, or to blow steam through them, until the desired effect be produced. Air freely employed for some time, instead of steam, succeeds adwith many oils, and its use has the advantage of not introducing moisture into the article. Another method is to boil oil or fat, for 15 to 30 minutes, with a little water and calcined magnesia. fat for a few minutes with powdered slipperyelm bark, in the proportion of 1 drachm of the powder to one pound of fat. The bark shrinks and gradually subsides, after which the fat is poured off. odor like that of the hickory-nut.

It communicates an thus treated has been kept unchanged for a Butter year.

Use in Lamps. 1494. To Purify Vegetable Oil for ounces alum, dissolved in 9 pounds of boiling Use in Lamps. To 100 pounds oil add 25 water. After stirring it about half an hour, .

After stirring it about half an hour, add 15 ounces nitric acid, still continuing to stir it. Let it stand 48 hours, when the fine oil will swim on the surface, and then draw it off. Such oil is used all over Continental the light of whale and fish-oil, without its Europe, and an equal quantity yields double offensive odor Lubricating Oils. Mr. Bancroft's process 1495. Bancroft's Process for Refining for refining common olive oil, lard oil, &c., for lubricating purposes, is to agitate them with from 35 with from 3½ to 8 per cent. caustic soda lye, 1.2 specific gravity. If, on trial of a small quantity, the lye be found to settle clear at the bottom, enough has been added. soapy matter to subside; the supernatant oil oil is allowed to rest for 24 hours, for the The 1491. To Prevent Oils and Fats from Becoming Rancid. The tendency of oils is then filtered. (See No. 1551.) Another and fats to become rancid may be prevented, plan of purifying oils is to agitate them with or greatly retarded, by artificial means.

One a strong solution of common salt. 1496. Calvert's Tests for the Purity 1500. To Test the Purity of Olive of Oils. In the use of the following tests, Oil. Cooley says: When pure olive oil is the result of a series of experiments by Mr. shaken in a phial only half filled, the bead F. G. Calvert, he recommends especial care or bubbles formed very rapidly disappear, in the preparation of the reagents used for but with the adulterated oil they remain testing, not only as regards their exact much longer before they burst. If olive strength and purity, but also in following oil contains + part of poppy oil, part of strictly the prescribed method of using them, it remains liquid at 36° Fahr., its prop. carefully noting the time required for their er freezing temperature; and if it conaction and effects to become apparent. tains of poppy oil, it does not solidify at 1497. Calvert's Caustic Soda Test all, unless cooled much below the freezing for Oils. A solution of caustic soda, specific gravity 1.340, is useful to distinguish fish from other animal and vegetable oils, owing to the distinct red color which the fish oil assumes; the presence of 1 per cent. of fish oil point of water. Pure olive oil well agitated for some time with of its volume of nitric solution of mercury, becomes quite solid in 3 or 4 hours, without any separation of liquid oil. (The mercurial solution is made by dissolving will be detected by the test. Add one vol- 1 ounce mercury in 2 fluid ounces 14 drachms ume of the test to 5 volumes of the oil, well nitric acid specific gravity 1.500.) According mixed, and heated to the boiling point. to M. Boudet, 1 grain of hyponitrous acid Hempseed oil acquires a brown-yellow color, (hyponitric?) mixed with 3 grains of nitric and becomes SO thick as to entirely lose its acid, will cause the perfect solidification of fluidity. Linseed oil assumes a much bright- 200 grains of pure olive oil in 75 to 78 miner yellow color, and remains fluid. India utes. nut oil, gallipoli oil, and pale rape oils, become a solid white mass in 5 minutes, while the other oils remain fluid.

1498. Calvert's Sulphuric Acid Tests for Oils. I. Sulphuric acid of specific gravity 1.475 will detect oils adulterated with hempseed and linseed oils to the amount of 10 per cent. Fish oil may be detected to the amount of 1 per cent. by the red color it assumes, this being noticed more particularly when the fish oil is allowed to separate by standing. To apply the test agitate 1 volume with 5 volumes of the oil, and allow the mixture to stand for fifteen minutes.

II. For the detection of hemp, linseed, fish, gallipoli, and French nut oils, 1 volume 1501. To Test the Purity of Castor Oil. Castor oil is frequently adulterated with rape oil; but this may be detected by its not dissolving in strong alcohol, and also by its less density. Pure castor oil is soluble in an equal weight of alcohol specific gravity 0.820. 1502. Το Refine Olive Oil. Olive oil intended for huiles antiques (see No. 1244) and other like uses, is commonly refined by violently agitating it in glass or stoneware, with about 1½ to 2 per cent. of its weight of concentrated sulphuric acid. This renders it opaque, and causes it to assume a greenish color. After about 2 weeks' repose, it deposits much coloring matter, and is then found of sulphuric acid of specific gravity 1.530, to have acquired greater fluidity, to have beagitated with 5 volumes of oil, and the mixture allowed to stand for 5 minutes. Under this test the above mentioned oils alone assume a decided coloration. III. Sulphuric acid of specific gravity 1.635, used similar to the preceding, and the effects noted after standing 2 minutes, affords a test under which the colorations are distinct and well marked, and will detect 10 per cent. of rapeseed oil in olive oil, of lard oil in poppy oil, of French nut oil in olive oil, and of fish oil in neat's foot oil.

A stronger acid than this carbonizes the oils and destroys the coloration. 1499. Calvert's Nitric Acid Tests for Oils. The successive application of nitric acid of specific gravity 1.330, and of a solution of caustic soda of specific gravity 1.340, can be successfully applied to detect the following very frequent cases of adulteration: I. Gallipoli oil with fish oils; the former assumes no distinct color with the acid, and gives with soda a mass of fibrous consistency, while fish oils are colored red, and become mucilaginous with the alkali.

II. Castor oil with poppy oil; the former, if adulterated, acquires a reddish tinge, and the mass with the alkali loses much of its fibrous appearance.

III. Rapeseed oil with French nut oil; under the nitric acid test the former, if adulterated, assumes a reddish tinge, more or less intense, which alkali increases, and renders the semi-saponified mass more fibrous. come much paler, to be more emollient and glossy as a lubricator, and to burn with great er brilliancy. The clear portion is now de. canted, well washed with steam or hot water, and, after sufficient repose in a close vessel, at a temperature about 60° Fahr., again decanted, and, if necessary, filtered through Canton flannel or bibulous paper. This plan is also applied to other fixed oils, and answers well for most of the recently expressed vegetable oils. 1503. To Purify and Sweeten Castor Oil. The American Journal of Pharmacy gives the following receipt for this purpose:

Take 1000 parts of the oil, 25 parts purified bone-black, 10 parts calcined magnesia. Mix them carefully in a convenient vessel of glass or tinned iron, and let it stand during 3 days, with occasional agitation, and filter through paper or felt. (See No. 1504).