BOUILLON. 95 



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 [Centralb. f. Bald. u. Fnrasit- 

 enkunde, 1891, Bd. x., Nos. 2 and 3) recommends exact 

 titration with a solution of caustic soda. For this pur- 

 pose 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 clown 

 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 



