1499. Calvert's Nitric Acid Tests for Oils

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.

1500. To Test the Purity of Olive Oil

1500.    To Test the Purity of Olive Oil. Cooley says: When pure olive oil is shaken in a phial only half filled, the bead or bubbles formed very rapidly disappear, but with the adulterated oil they remain much longer before they burst. If olive oil contains 1/4 part of poppy oil, part of it remains liquid at 36° Fahr., its proper freezing temperature; and if it contains 1/3 of poppy oil, it does not solidify at all, unless cooled much below the freezing point of water. Pure olive oil well agitated for some time with 1/12 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 1 ounce mercury in 2 fluid ounces 11/2 drachms nitric acid specific gravity 1.500.) According to M. Boudet, 1 grain of hyponitrous acid (hyponitric?) mixed with 3 grains of nitric acid, will cause the perfect solidification of 200 grains of pure olive oil in 75 to 78 minutes.

1501. To Test the Purity of Castor Oil

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. To Refine Olive Oil

1502.    To Refine Olive Oil. Olive oil intended for huiles antiques {see No. 1244 (French Huiles or Hair Oils)) and other like uses, is commonly refined by violently agitating it in glass or stoneware, with about 1 1/2 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 to have acquired greater fluidity, to have become much paler, to be more emollient and glossy as a lubricator, and to burn with greater brilliancy. The clear portion is now decanted, 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.