THE METHODS OF GAUTIES. AND ETABD. 233 



formation of a deposit or a pellicle in the fluid. By regulating 

 the amount of air entering through this tube, more or less of 

 a vacuum will be formed in the flask. After evaporation to a syrup, 

 an extraction is made with 96 per cent, alcohol and the filtered ex- 

 tract is treated with a warm alcoholic solution of lead acetate. The 

 lead precipitate is removed by filtration, the filtrate evaporated to a 

 syrup and again extracted with 96 per cent, alcohol. The alcohol 

 is driven off; the residue taken up with water; traces of lead re- 

 moved with hydrogen sulphid ; and the filtrate, acidified with hy- 

 drochloric acid, evaporated to a syrup, which is extracted with alco- 

 hol, and the filtrate precipitated with an alcoholic solution of mer- 

 curic chlorid. The mercury precipitate is boiled with water, and on 

 account of the differences in solubility of the double compounds with 

 mercury, one ptomain may be separated from others at this stage of 

 the process. (If thought best, the lead precipitate may be freed 

 from lead and carried through the subsequent steps of the process. 

 Brieger found small quantities of ptomains in the lead precipitate 

 only in his work with poisonous mussels.) 



The mercury filtrate is freed from mercury, evaporated, and the 

 excess of hydrochloric acid carefully neutralized with soda (the re- 

 action is kept feebly acid) ; then it is again taken up with alcohol in 

 order to free it from inorganic salts. The alcohol is evaporated, 

 the residue taken up with water, the remaining traces of hydrochloric 

 acid neutralized with soda, the whole acidified with nitric acid, and 

 treated with phosphomolybdic acid. The phosphomolybdate double 

 compound is separated by filtration and decomposed with neutral 

 acetate of lead. This is hastened by heating on the water-bath. 

 The lead is removed by hydrogen sulphid, the filtrate is evaporated 

 to a syrup and taken up with alcohol, from which many ptomains 

 are deposited as chlorids, or double salts may be formed in the 

 alcoholic solution. The chlorids as deposited from the alcoholic solu- 

 tion are seldom pure and may be isolated by precipitation with gold 

 chlorid, platinum chlorid, or picric acid, and on account of the dif- 

 ference in solubility of these double salts, the process of purification 

 is rendered more easy. The chlorid of the base is obtained by re- 

 moving the metal with hydrogen sulphid, while the picrate is taken 

 up with water, acidified with hydrochloric acid, and repeatedly ex- 

 tracted with ether, in order to remove the picric acid. 



The Methods of Gautier and Etard. — The putrid matters, 

 liquid and solid, are distilled at a low temperature in vacuo. The 

 distillate (A) may contain ammonium carbonate, phenol, skatol, 

 trimethylamin, and the volatile fatty acids. The residue after fil- 

 tration is treated successively by ether and alcohol. 



The extraction with ether [B) separates the ptomain and some 

 fatty acids. The alcoholic extract (C) removes the remainder of the 



