(30 BACTERIOLOGY. 



is accomplished with the saturated soda solution, and 

 the reaction is detected with the ordinary red and blue 

 litmus paper. 



Soda solution is not so good as a strong solution of 

 caustic soda or potash, because the carbonic acid liberated 

 from the sodium carbonate is frequently seen to give rise 

 to a confusing temporary acid reaction which disappears 

 on heating. To obviate this, Schultz ( Centralbl. f. Bad. 

 u. Parasitenkunde, Bd. x., Nos. 2 and 3, 1891) recom- 

 mends 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 whole volume is 

 exactly measured. 



From it 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 is added. Schult/ 

 recommends 1 drop of phenolphtalein solution (1 

 gramme 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 into it, very slowly, 

 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 soda solution required for 

 each sample deviate but very slightly or not at all 

 the one from the other, the mean of these amounts is 

 taken as the amount of the soda solution necessary to 

 neutralize the quantity of bouillon employed. If 10 c.c. 



