294 M. D'Arcet 07i the Bones of Butcher's Meat. 



The ebullition of the rasped bones with water under the 

 pressure of the atmosphere has not the same inconvenience ; 

 but the operation is long and expensive, and the bones do not 

 give out nearly the quantity of gelatine which they can fur- 

 nish. 



About fifteen years since I discovered the art of extracting 

 the gelatine of bones by means of acids. The happiest results 

 were obtained; and if the direction of it had been placed in able 

 hands, there is no doubt that the preparation of gelatine as an 

 alimentary substance would since that time have acquired the 

 greatest extension. 



In considering about the same period the inconveniences of 

 Papin''s method, I was enabled to overcome them by modifica- 

 tions, the property of which I have secured by a patent which 

 was lately published. (Vol. xiv. of Patents and Inventions^ 264.) 



The process which appears to me the most advantageous is 

 that of exposing the bones to the action of steam having a 

 weak tension. Its success is caused by the steam condensing 

 in the pores of the bones ; it expels the fat, and then dissolves 

 successively all the gelatine. This is merely the repetition of 

 an old pharmaceutic process now forgotten, but which may be 

 found quoted in the Pharmacy of Baume, p. 108. Edition of 

 1790. 



The presence of fat in the bones makes the process compli- 

 cated. This fat becomes acid by the carbonate of lime which 

 they contain, under the influence of the condensed steam, and 

 forms an insoluble soup which prevents the dissolution of the 

 gelatine. It follows in consequence that the bones are de- 

 prived of this fat before the gelatine is separated. 



We come to this result by boiling the broken bones in wa- 

 ter in a copper uncovered, as is usually done, or by exposing 

 them at first only to the steam not condensed. 



The extraction of the gelatine by steam little condensed 

 requires at least four days to complete it. The broken 

 bones, deprived of their fat or not, are placed in a cylindrical 

 basket of tinned iron wire, filling almost entirely the capacity 

 of a metallic cylinder in which it is held suspended. 



This being closed, steam of a weak tension is introduced, 

 which melts the fat, and dissolves a little of the gelatine. We 



