182 CHEMICAL MANUEES. 



constitutes an excellent food for animals and a very active chemical 

 manure for meadows. 



The fat extracted from bones by steam has perceptibly the same 

 colour as that got by boiling, but it is of better quality and gives off 

 a less unpleasant smell. When the bones treated have begun to 

 decompose, as very frequently is the case, the volatile bad smelling 

 products are in great part volatilized during the operation. Bang 

 and Ruffin have suggested steaming combined with centrifuging. 

 The fat with a little gelatine can first be extracted in a centrifugal 

 machine, then the gelatine. This process has not been adopted by 

 bone-boilers, but it is used in extracting fat from fish. 



Extraction of Fat from Bones by Benzine. — For a long time 

 efforts were made in France to extract fat from bones by benzine. 

 Deiss used carbon disulphide, but as the bones, the fat of which was 

 extracted by this solvent, gave bad quality glues, the process hardly 

 extended. In 1871, Vohl suggested canadol (gasolene) as an advan- 

 tageous substitute for carbon disulphide ; then in 1876 M. Terne took 

 out a patent for extraction by petroleum benzine, in America, w^hence 

 this industry spread to Europe. Petroleum benzine presents, in fact, 

 less danger than carbon disulphide, and its condensation is more 

 easy because it boils at a higher temperature. The apparatus con- 

 structed by Mr. Deroy, sen., for extracting fat from bones by 

 petroleum benzine consists essentially (Fig. 36) (1) of an extractor 

 A with a perforated false bottom, and steam coil ; (2) of a re- 

 cuperator B or distilling pan; (3) of a condenser C; (4) of a 

 pump E for circulating the solvent. Working. — The routine of the 

 operation may be resumed thus. A certain amount of water is run 

 into the extractor according to the capacity of the apparatus, so as to 

 preserve the coil and the taps from the attack of fatty acids. After- 

 w^ards, the extractor is charged with crushed bones free from foreign 

 matter. As soon as the charge amounts to a quarter of the capacity 

 of the apparatus, the pump is started, and a beginning made by 

 drenching with benzine the bones introduced. During this time 

 the autoclave is charged in such a way that the solvent constantly 

 bathes the bones, which enables the interposed air to escape freely. 

 When the apparatus is full the top stopper of the extractor is closed 

 and the tap 23 on the condenser opened. The air is allowed to 

 escape until condensed benzine appears ; the tap is then turned and 

 the pressure allow^ed to rise to 1| kgs. on the manometre (9). 

 This pressure once reached, the steam tap is closed and the ap- 

 paratus allowed to rest till morning. The benzine is charged with 

 all the fat of the bones, and the vapours are totally condensed. The 

 next morning the a]3paratus is emptied into the distilling pan, and 

 after a rest — about ten minutes — the w^ater, previously run into the 

 autoclave, and w^hich now occupies the bottom of the pan, is with- 

 drawn. The benzine is then recovered by distillation and by pass- 



