444 Q/i ike Use of Animal Einpyreiimalic Oil. 



use has been made : for we cannot consider as of much conse- 

 tjuencc tlic very trifling quantities of this article which are annu- 

 ally employed in pharmacy, and there is no other known con- 

 sumption of it. 



I have succeeded in obtaining with this oil a lye for the prepa- 

 ration of Prussian blue, which is as rich in colouring matter as 

 that made of horns or with blood ; it is a blue equally beautiful 

 and clear. 



The consistence of the blue precipitate which Diesbach ob- 

 tained in endeavouring to prepare Florence lac with salt of tartar 

 which he had got from Dippel, bad induced some chemists to 

 treat this salt with animal empvreumatic oil in the bope of con- 

 verting it into prussiate of potash ; but their experiments, which 

 were made in the liquid way, had not any success, and could not 

 have any ; for, besides that in the animal oils the elements of the 

 prussic acid are in a different state than in that acid, these che- 

 mists wanted the principal condition necessary to the acids form- 

 ing and uniting itself to the alk:di — namely, that ot operating on 

 it with a red heat. 



I have followed the direct method, which was to reduce into 

 charcoal by calcination the animal oil, and to redden this char- 

 coal witii alkali. The result was a prussiate, which, with the sul- 

 phate of iron and the sulphate of potash and alumine, yielded a 

 Very beautiful and abundant blue. 



It would be wrong to rank in the same class for the improve- 

 ment of the Prussian alkali the charcoal which remains after the 

 distillation of animal matters for the purpose of extracting am- 

 monia from them. The latter charcoal has experienced too strong 

 an ignition for the elements of the prussic acid to be able to 

 maintain an affinity favourable to the production of the acid by 

 the calcination of charcoal with the alkali. 



Chemists mav by means of empyreumatic oil procure, in a 

 little time and without being incommoded by the least odour, a 

 prussiate of potash fit for serving as a reactive. For this purpose 

 let them half fill with the animal oil a Hessian crucible of the ca- 

 pacity of from 8 to 16 ounces, and place it among burning char- 

 coal. As soon as the oil begins to simmer, withdraw the crucible 

 from the furnace and place it on the ground under the chimney, 

 covering itwith a leather pipe such as may, if necessary, be length- 

 ened. The object of this covering is to promote the combustion, 

 and the better to conduct away the smoke. In proportion as 

 the oil is consumed let more oil be of new introduced into the 

 crucible ; and when the whole has been consumed, calcine the 

 residue at a gentle red heat until a brown vapour begins to ascend, 

 and till a portion of the mass put upon a cold body hardens on 

 the instant, and presents the appearance of a porous and friable 

 body, without any odour. LXXV. Notices 



