412 



easily decomposed, and when treated with alkalies or ammonia, yield a 

 splendid and durable red solution which, by a subsequent treatment, 

 becomes the jet black, amorphous, pure regiauic acid. 



YoHL ON EXTRACTION OF FATS. — Much difficulty is experienced in 

 keeping laid and other animal fats for any considerable length of time, 

 without their becoming rancid or acquiring some accessory taste which 

 renders them less fit for use. This rancidity results from several gen- 

 eral causes, in most cases in consequence of the i)resence of water, or 

 from a mixtiu-e of some nitrogenous substance. These fats are gen- 

 erally obtained in two different ways: In one, the raw fat is boiled with 

 water, the clear, melted fat skimmed off, and the remaining water re- 

 moved by adding pulverized salt, or otherwise. In the other the fat is 

 cut into pieces after it has been washed with water, and heated, without 

 water, at an elevated temperature, either with or without the addition 

 of salt. In the first instance there is usually a considerable percentage 

 of animal matter, especially of gelatine and fibrin, mixed with a certain 

 percentage of water, which speedily pass into decomposition. In the 

 second case, although this difficulty is less troublesome, there is almost 

 always a burnt taste and more or less of color, while rancidity is less 

 common. 



In a late article. Dr. Yohl, of Cologne, presents what he considers a 

 greatly imi^roved method for the extraction of animal oils, so as to have 

 them entirely free from the foreign substances referred to, and conse- 

 quently not liable to change. For this purpose the fresh, raw fat is to 

 be freed as completely as possible from the adherent particles of flesh 

 and skin, and cut up into thin slices or small cubes. These are then to 

 be washed with cold water (as free as possible from lime) until this runs 

 off entirely colorless and no i^articles of blood remain in the fat. When 

 properly drained off this washed fat is to be placed in a cylindrical tub- 

 shaped stoneware vessel of about four feet in height and a foot and a 

 half in diameter, which is inserted in a water-bath, which can be heated 

 by steam to the melting point of the fat. At the bottom of the vessel 

 is a cock of wood, earthenware, or x)orcelaiu, so attached that the ves- 

 sel can be emptied while in the bath. After the vessel is filled to about 

 three-fourths of its capacity with raw fat, a sieve like perforated disk of 

 stoneware is to be laid upon the surface of the pot, and 10 per cent, of 

 extremely diluted and chemically ]jure hydrochloric acid added, in a 

 proportion of 3 pounds of the acid (of 1.12 specific gravity) to 100 pounds 

 of water. The vessel is then to be covered with a well-ground and 

 tightly fitting stoneware top. By heating, the fat is melted in the cells, 

 the membranous walls of which are dissolved bj' the diluted acid, allow- 

 ing the fat to escape, which rises above the disk, this at the same time 

 gradually sinking toward the bottom. All the membranous, unmelted 

 portions'are carried down under it and accumulate at the bottom with 

 .the dilute acid. 



"When all the fat is melted and all the membranous portions destroyed, 

 the acid liquid is to be let off and the fat washed two or three times 

 with hot water. (This acid gelatiuous solution can be converted into an 

 excellent manure by the addition of a powdered phosphorite.) A small 

 quantity of carbonate of magnesia is to be added in the last washing, 

 so as to completely remove the acid. The fat, thus washed, is now to 

 be dissolved in its volume, or less, of canadol, in the course of which 

 the water and nitrogenous animal substances are removed, and may be 

 separated, by decanting. The clean fatty solution is now to be intro- 

 duced into a tinned copper distilling apparatus, and the solvent again 



