160 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



The extiaction of the first distillate is best done in a sepa- 

 rating-funnel and in separate portions of about 300 cc. with 

 200 cc. of ether. After shaking vigorously draw off the 

 aqueous fluid (B) and pour into the separating-funnel a new 

 quantity of the distillate, etc. Since the ether is dissolved 

 to some extent by water, some fresh ether is to be added each 

 time. 



When the entire distillate has been extracted, place all 

 the aqueous fluid (B) in a large dish and let it stand until the 

 dissolved ether has volatilized spontaneously, then evaporate : 

 there remains a white mass of salts, which consist very largely 

 of ammonium chloride. 



The ether solution (A) is now very thoroughly shaken 

 with the same volume of water and 50 cc. of sodium hydrox- 

 ide solution. The volatile acids formed in the putrefaction 

 are dissolved in the alkaline solution (D), while indol and 

 also skatol remain in the ether solution. Distil off most of 

 the ether from the ether extract (now designated (C) ) at a 

 gentle heat on the water-bath, and let the residue evaporate 

 spontaneously. Impure indol remains. For the reactions 

 of this substance see page 169. 



The alkaline solution (D) is again acidified with hydro- 

 chloric acid, sodium carbonate solution added until the fluid 

 reacts acid only from the carbonic acid or is neutral (a por- 

 tion taken out and heated must show an alkaline reaction 

 when cold), and the mixture shaken with ether. Phenol 

 and cresol are dissolved by the ether, while the volatile fatty 

 acids remain in the aqueous fluid as alkali salts. As carbon 

 dioxide is evolved on shaking, considerable pressure develops 

 in the separating-funnel; it is therefore necessary to be cau- 

 tious and to remove the stopper repeatedly or to reverse the 

 separating-funnel and open the stop-cock. The ether extract 

 (E) is then separated from the aqueous fluid (F). The 

 ethereal solution (E), whe"n evaporated, leaves an impure 



