ALCOHOL PRODUCTION 285 



Buff precipitate = benzoic acid, and other acids re- 

 lated to benzoic acid. 



Violet colour = salicylic acid. 



Inky black colour or precipitate = gallic acid or tannic 

 acid. 



For further identification the melting-points of the 

 crystalline acids, and the percentage of silver in their 

 silver salts should be determined. 



3. Ammonia Production. 



Medium- Required: 



Nutrient bouillon. 

 Reagent Required: 



Nessler reagent. 



METHOD. 



1. Prepare cultivation in bulk (100 c.c.) in a 250 c.c. 

 flask and incubate together with a control flask. 



Test the cultivation and the control for ammonia 

 in the following manner: 



2. To each flask add 2 grammes of calcined mag- 

 nesia, then connect up with condensers and dis,til. 



3 . Collect 50 c.c. distillate, from each, in a Nessler glass. 



4. Add i c.c. Nessler reagent to each glass by means 

 of a clean pipette. 



Yellow colour = ammonia. 



The depth of colour is proportionate to the amount 

 present. 



4. Alcohol, etc., Production. Divide the distillate 

 "A" obtained in the course of a previous experiment 

 (vide page 282, step 3) into four portions and test for 

 the production of alcohol, acetaldehyde, acetone. 



i. Add Lugol's iodine, then a little NaOH solution, 

 and stir with a glass rod till the colour of the iodine 

 disappears. 



Pale-yellow crystalline precipitate of iodoform, with 

 its characteristic smell, appearing in the cold, indicates 

 acetaldehyde, or acetone; appearing only on warming 

 indicates alcohol. 



