78 BACTERIOLOGY. 



tion. Ordinarily, this is accomplished with the saturated 

 sodium carbonate solution, and the reaction is deter- 

 mined with the ordinary red and blue litmus papers. 



The sodium carbonate 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 confusing, temporary acid 

 reaction which disappears on heating. To obviate this, 

 Schultz (Centralbl f. Bald. u. Parasitenkunde, 1891, 

 Bd. x., Nos. 2 and 3) 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 boil- 

 ing and filtration, and has cooled down to the temper- 

 ature 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 this a few drops of one of the indicators commonly 

 employed in analytical work is added. Schultz recom- 

 mends 1 drop of phenolphthalein solution (1 gramme 

 phenolphthalein in 300 c.c. of alcohol) to 1 c.c. of bouil- 

 lon. 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 caustic 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 alkali necessary to neutralize the quantity 

 of bouillon employed. If 10 c.c. of bouillon were em- 



