EXPERIMENT STATION BULLETINS. 



619 



to the flasks and their densities adjusted to 1.0900 ± 0.0001 at 20° 

 ± 0.5 using a pyenometer. 



For analysis, 25 c.c. samples were diluted to 250 c.c. and 10 c.c. 

 aliquots used for the determinations. The ammonia was estimated by 

 the distillation method and the citric acid by titration after the addition 

 of formaldehyde, all determinations being made in triplicate. The 

 averages are given in the following table: 



^Neutralized by ordinary technic. See p. 13. 



While such differences may appear to be large, it should be stated 

 that the extreme readings for the whole series were 26.41 and 26.87 

 c.c. N/10 HCl for the ammonia determinations and 26.72 and 27.03 

 c.c. N/10 NaOH for the citric acid estimations. A '^neutral" solution 

 of ammonium citrate may then he defined as one in which the ratio of 

 NH^ :C^n,0, is 1 : 3.794. At 20° such a solution containing 45.33 g. 

 NH3 and 172.00 g. CeHsO, per liter will have a density of 1.09. 



Of the solutions analyzed by McOandless the three which were neutral 

 to coralline were actually very close to the point of absolute neutrality, 

 much closer in fact than the one which he selected as a standard. Here 

 again however is a case of the confusion of the two solutions, one neutral 

 itself in reaction and the other a solution of the neutral salt. 



Four solutions of ammonium citrate were next made and carefully 

 adjusted to a S. G. of 1.09 and reactions respectively of 6.6, 7.0, 7.4 and 

 7.8. The indicators used for the adjustment of the reaction of these 

 solutions were brom thymol blue for the first, phenol red for the second 

 and third and cresol red for the fourth. The last one could not be held 

 constant for any length of time because of loss of ammonia. It was 

 however always within 0.05 Ph of the indicated value. Their composi- 

 tions are given in the following table: 



