L. TECHNOLOGY. 475 



accomplished by means of a stirrer in the form of a screen or 

 sieve. The alcoholic lye should be freshly prepared before 

 each operation. 8 A, August, 152. 



VOHL OX EXTRACTION OF FATS. 



Much difficulty is experienced in keeping lard 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 sev- 

 eral general causes, in most cases in consequence of the pres- 

 ence of water, or from a mixture of some nitrogenous sub- 

 stance. These fats are generally obtained in two different 

 ways : In one, the raw fat is boiled with water, the clear, 

 melted fat skimmed off, and the remaining water removed 

 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 per- 

 centage of water, which speedily pass into decomposition. In 

 the second case, although this difficulty is less troublesome, 

 there is almost always a burned taste, and more or less of 

 color, while rancidity is less common. 



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

 considers a greatly improved method for the extraction of 

 animal oils, so as to have them entirely free from the foreign 

 substances referred to, and consequently not liable to change. 

 For this purpose, the fresh, raw fat is to be freed as complete- 

 ly 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 particles of blood 

 remain in the fat. When properly drained off, this washed 

 fat is to be placed in a cylindrical tub-shaped stone-ware ves- 

 sel of about four feet in height, and a foot and a half in di- 

 ameter, which is inserted in a water-bath, which can be heat- 

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

 of the vessel is a cock of wood, earthen-ware, or porcelain, so 

 attached that the vessel can be emptied while in the bath. 

 After the vessel is filled to about three fourths of its capac- 



