1913] Solutions of Ammonium Citrate 31 



The experiments were carried out in a Dewar flask of about 

 200 cc. capacity, provided with a platinum stirrer and a ther- 

 mometer graduated to tenths of degrees. The citric acid and 

 ammonia solutions were the same as those used in the former 

 method. Again, 100 cc. of citric acid solution was partially 

 neutralized with 36 cc. of ammonia solution in an ordinary 

 beaker. The cooled solution was then poured into the Dewar 

 flask. The beaker was washed several times with water and 

 the washings poured into the Dewar flask, so that the final vol- 

 ume of solution was about 150 cc. Just as in the previous 



method, the ammonia solution was added from a buret provided 

 with a small delivery tube, which extended to the bottom of the 

 flask. Ammonia was now added in portions of 0.5 cc. and the 

 mixture stirred for about I/2 minute. After IY2 minutes no 

 further rise of temperature was noticed. After each addi- 

 tion of 0.5 cc. of ammonia there was a constant rise of 

 temperature of about 0.40° until the buret reading was 

 39.50 cc. of ammonia. For the next 0.5 cc. of ammonia 

 the rise of temperature was only 0.16°. Beyond 40 

 cc. practically no change in temperature occurred. The 

 neutral point is therefore between 39.5 cc. and 40 cc. of am- 

 monia. The exact neutral point is found by plotting tLe 

 curve, using the number of cc. of ammonia as abscissa and the 



