[22] By the term “hepatic aloes” I mean the opaque liver-colored aloes imported into England from the East Indies (usually from Bombay). This sort of aloes is very different from the hepatic Barbadoes aloes, which formerly appears to have been exclusively called “hepatic aloes.”
THE CHEMICAL COMPOSITION OF COD-LIVER OIL. BY DR. H. L. WINCKLER.
Of all the drugs which have been introduced into medical practice within the last ten years, none has excited so much attention, and has met with so favorable a reception, as cod-liver oil. To what principles its peculiar properties are to be referred, has not yet been ascertained. By some they have been attributed {241} to the presence of a small quantity of iodine; but this has not proved a satisfactory explanation. Many chemists have endeavoured to solve this problem, but without success.—Amongst others, Dr. de Jongh, who attributed its virtue to gaduin—a new principle which he had discovered in the oil, with the usual fatty acids, and some of the constituents of bile, and traces of iodine and bromine.
The results of my researches are different, in an important degree. According to my experience, cod-liver oil is an organic whole of a peculiar character, differing in its chemical composition from any of the fat oils which have been heretofore applied to medical purposes.
The evidences for this conclusion are the following:—
1. When the clear, pale cod-liver oil is saponified with potash, and the resulting soap treated with tartaric acid, oleic and margaric acids are obtained.
2. When a mixture of six parts of caustic potash, twenty-four parts of distilled water, and twenty-four parts of cod-liver oil, after being allowed to remain at an ordinary temperature, and often shaken, and finally diluted with twenty-four parts of distilled water, is distilled, a distillate is obtained, which possesses an intense odor of cod-liver oil, and contains an appreciable quantity of a peculiar organic compound, namely, oxide of propyl.
3. When nine parts of cod-liver oil are saponified with five parts of oxide of lead, with the necessary quantity of distilled water, in a porcelain vessel, by the heat of a water bath, the oil is decomposed into oleic and margaric acids, and a new acid propylic acid. The chief part of this acid combines, like the oleic and margaric acids, with the oxide of lead, as it appears, to form a basic compound; and another lead salt, probably an acid one, can be washed out of the plaister with distilled water. It is worthy of remark, that no glycerine is formed in this process. The plaister smells of train oil and herrings; and when it is exposed in a thin layer to the action of the atmosphere in a water bath, it becomes colored dark brown, after the {242} evaporation of the water; and by the same means it loses its penetrating odor. The cause of the coloring is due to the strong disposition which the salts of propylic acid possess to oxidize, and consequently, to become brown. When the solution of the acid propylate of lead is treated with sulphuretted hydrogen, after the separation of the sulphuret of lead, is obtained an entirely colorless and strongly acid reacting solution, which by evaporation in a water bath, becomes by degrees colored. At the commencement of the last part of the operation it loses its penetrating odor, and at last leaves a dark brown residue. Exactly in the same manner, the watery solutions of neutral propylates of barytes and ammonia behave themselves. The neutral, colorless, and undecomposed ammoniacal salt smells of herrings; and the baryta salt, as concentrated decoction of meat.
4. When the before-described (No. 2) solution of cod-liver oil soap is thrown into a capacious distillery apparatus, with the addition of caustic lime and chloride of ammonium, (in the proportion of six drachms of caustic potash, three ounces of cod-liver oil, six ounces of water, six ounces of fresh burnt lime, and one drachm of chloride of ammonium,) with the precaution, that the mixture of lime and chloride of ammonium be not added until the soap is formed in the retort, so that it may penetrate thoroughly the mass, and the distillation proceeded with by means of a gentle heat, as the formation of hydrate of lime evolves considerable heat, there distils rather quickly a clear, watery fluid, over which is a concentrated solution of propylamin free from ammonia. By saturating this solution with diluted sulphuric acid, and adding alcohol, sulphate of propylamin readily crystallizes out of it.