BOUILLON. 105 



portant is the neutralization. Ordinarily, this is ac- 

 complished with the saturated sodium carbonate solu- 

 tion, and the reaction is determined with red and blue 

 litmus papers ; for the beginner this method serves most 

 purposes. 



The sodium carbonate solution is not so good, how- 

 ever, as a strong solution of caustic soda or potash, 

 because the carbonic acid liberated from the sodium 

 carbonate frequently gives rise to a confusing, tem- 

 porary acid reaction which disappears on heating; 

 nor is litmus the most reliable indicator to employ. 

 To obviate this, Schultz 1 recommends exact titration 

 with a solution of caustic soda. For this purpose a 4 

 per cent, solution of caustic soda is prepared. From this 

 a 0.4 per cent, solution is made, and with it the titration 

 is practised. After the bouillon has been deprived of all 

 coagulable albumin and blood-coloring-matter by boiling 

 and filtration, and has cooled down to the temperature 

 of the air, 'its volume is exactly measured. 



From this a sample of exactly 5 or 10 c.c. is then taken, 

 and to it a few drops of one of the indicators com- 

 monly employed in analytical work are added. Schultz 

 recommends 1 drop of phenolphtalein solution (1 

 gramme of phenolphtalein in 300 c.c. of alcohol) to 1 

 c.c. of bouillon. The beaker containing the sample is 

 placed upon white paper, and the dilute caustic soda 

 solution is then allowed to drop very slowly into it 

 from a burette, until there appears a very delicate rose 

 color, which indicates the beginning of alkaline reaction. 

 A second sample of the bouillon is treated in the same 

 way. If the amounts of caustic soda solution required 



1 Schultz: Ccntralbl. f. Bakt. u. Parasitenkmide, 1891, vol. x. Nos. 



