HANDBOOK FOR BIO-CHEMICAL LABORATORY. 43 



residue, previously treated with some caustic-soda solution, is 

 distilled in a current of steam* until no more indol passes over. 



The distillate is now shaken with ether, the ethereal solu- 

 tion distilled at the lowest possible temperature, and the 

 residue allowed to evaporate in a deep vessel until, on being 

 allowed to cool, it solidifies as a crystalline mass. The latter 

 is then dried in a desiccator over sulphuric acid. (E. and H 

 Salkowski.) The crystals thus obtained, consisting of indol 

 and skatol, are dissolved in a very small quantity -of absolute 

 alcohol and then treated with 8-10 vols. water. The skatol is 

 precipitated, but not the indol. The skatol is filtered off and 

 recrystallized from ether. The indol is obtained from the 

 watery solution by extracting it with ether and allowing the 

 ether to evaporate spontaneously. 



The mass of crystals, consisting of indol and skatol, may be 

 separated from each other by means of fractional distillation 

 in a current of steam when the skatol passes over first. 



Skatol may also be obtained from this mixture of crystals 

 by dissolving about 0.5 grm. in a few drops of benzol and 

 adding 1.5 grm. crystallized picric acid and sufficient benzol 

 to dissolve all while being heated in a covered beaker-glass. 

 On cooling the mass solidifies to a red crystalline mass. Xow 

 add 2 vols. petroleum ether and stir, filter after 24 hours, 

 wash with petroleum ether, and allow the crystals to dry 

 in the air. Place the crystals in a distilling flask and 

 distill with dilute caustic soda, which decomposes the indol, 

 while the skatol passes over and is condensed. This skatol is 

 purified by recrystallization from ether. 



Properties. Indol crystallizes from hot aqueous solutions 



* The current of steam is best produced by filling a large flask two- 

 thirds with water which has been acidified with a few cubic centimetres 

 of dilute H 2 SO 4 and a few pieces of zinc, which by the action of the heat 

 develops a gentle current of hydrogen, which prevents bumping and 

 gives rise to a quiet, even generation of steam, which may be kept up 

 for hours. 



