Extraction of Animal Fats to be used either as Food or for Cosmetic Purposes.
By DR. H. VOHL.
The fresh fat is first as much as possible freed from membranes and flesh, next cut up either into small discs or cubes, and then thoroughly washed with cold water (which should contain the least possible quantity of lime, therefore fresh river, or, better, good rain-water, should be used) until all blood is entirely removed. The fat is next put into a cylindrical stoneware vessel, 1.25 metres high and 0.5 metre inside diameter, this vessel being placed in a water-bath and provided with a tap at the bottom, so placed that the vessel may be emptied without removing it from the water-bath. The vessel having been filled for three-fourths of its capacity with fat, there is placed on the top of it a stoneware perforated disc, and next poured over it (the fat) very dilute pure hydrochloric acid—10 per cent. of the weight of the fat of an acid made up of 3 lbs. of chemically pure HCl at 1.12 sp. gr. to 100 lbs. of water (sulphuric acid is not to be substituted., because its solvent power for membranes is very slight). This having been done, the stoneware vessel is closed with a well fitting cover, and the water-bath heated. From the fat, while melting, the perforated cover carries, by slowly sinking downwards, all the impurities, as far as they are not dissolved by the acid, which at the end of the operation is run off by aid of the tap. The fat is then, while yet molten, washed several times with warm water, to which, for the last washing, some carbonate of magnesia is added. The acid liquid yields, along with phosphorite or other native phosphate of lime, an excellent manure. The fat is next treated with Canada oil (a refined petroleum spirit), and the solution separated by decantation from any yet present nitrogenous organic matter (membranes, &c.). The solution of the fat is freed by distillation (in a water-bath) from the Canada oil, and the result is the production of a very superior fat, which, being absolutely free from water and other organic, especially nitrogenous matter, is not liable to become rancid, and may be preserved for many years. Although the process here briefly described may appear complicated, it yields not only a better, but also far larger quantity of product.—Chem. News., from Dingler's Polyt. Journ., Aug. 1st, 1871.