PREPARATION OF PEPTONES 2(X) 



barium. With very dilute solutions traces of these 

 compounds may escape detection. During the con- 

 centration of the solution, that of the sulphuric acid 

 and barium hydroxide naturally increases, so that we 

 may eventually get an hydrolysis of the peptone 

 mixture. 



Finally, we are left with a light yellow syrupy 

 residuum. The latter is mixed with about 100 times 

 its amount of methyl-alcohol, and the mixture 

 is boiled. The boiling hot solution is filtered 

 through a filter paper into about five times its 

 amount of cold ethyl alcohol. It is well to put 

 the latter into iced water. Precipitation is aided by 

 the addition of ether. The whole is filtered, directly 

 the precipitate begins to be formed. During the 

 filtration, the filter should not be allowed to become 

 empty. It is best to use a filter pump. Only at the 

 end is the liquid allowed to pass entirely through the 

 filter, after which the latter is immediately placed in 

 a vacuum exsiccator. After a day or two the peptone 

 is absolutely dry, and may then be weighed. First, 

 a 10 per cent, solution, in 0*9 per cent, solution of 

 common salt, is prepared, and the deviation of rota- 

 tion of the solution is determined. If this is more 

 than i, the solution is diluted, until it shows a rota- 

 tion of about 075. The higher degree of rotation 

 would not be injurious. Dilution is only effected in 

 order to make the best use of the costly material. 



