PHENOL PRODUCTION 287 



2. Add 2 c.c. paradimethylamino-benzaldehyde 

 solution. 



3. Add 2 c.c. potassium persulphate solution. 



The presence of indol is indicated by the appearance 

 of a delicate rose-pink colour throughout the mixture 

 which deepens slightly on standing. 



Indol is tested for in many laboratories by the ordinary 

 nitrosoindol reaction which, however, is not so delicate a method 

 as that above described. The test is carried out as follows: 



1. Remove the cotton- wool plug from the tube, and run in 

 i c.c. pure concentrated sulphuric acid down the side of the tube 

 by means of a sterile pipette. Place the tube upright in a rack, 

 and allow it to stand, if necessary, for ten minutes. 



A rose-pink or red colour at the junction of the two liquids = 

 indol (plus a nitrite). 



2. If the colour of the medium remains unaltered, add 2 c.c. of 

 a o.o i per cent, aqueous solution sodium nitrite, and again allow 

 the culture to stand for ten minutes. 



Red colouration = indol. 



NOTE. In place of performing the test in two stages as given 

 above, 2 c.c. concentrated commercial sulphuric, hydrochloric, or 

 nitric acid (all of which hold a trace of nitrite in solution) , may be 

 run into the cultivation. The development of a red colour within 

 twenty minutes will indicate the presence of indol. 



5a. Phenol Production. 



Medium Required: 



Nutrient bouillon. 

 Reagents Required: 



Hydrochloric acid, concentrated. 



Millon's reagent. 



Ferric chloride, i per cent, aqueous solution. 



METHOD. 



1. Prepare cultivation in a Bohemian flask contain- 

 ing at least 50 c.c. of medium, and incubate. 



Test for phenol in the following manner: 



2. Add 5 c.c., 25 per cent, sulphuric acid to the 

 cultivation and connect up the flask with a condenser. 



3. Distil over 15 to 20 c.c. Divide the distillate 

 into three portions a, b and c. 



4. Add to (a) 0.5 c.c. Millon's reagent and boil. 

 Red colour = phenol. 



