New York Agricultural Experiment Station. 295 



when treated with ammonium citrate at 65° C. for one-half hour 

 an indication as to the reason for the liberation of the ammonia 

 may be found. The fertilizing materials, after being extracted with 

 water, leave a residue which, in most cases, contains alkaline material, 

 alkaline phosphates, carbonates of calcium and magnesium and 

 oxides of other elements. These all tend to drive off ammonia from 

 the citrate solution. 



Table III.— Comparison of the Use of Ammonium Citrate and Sodium Citrate 

 for the Determination of Reverted Phosphoric Acid. 



It is realized that the small amount of evidence presented in this 

 paper does not settle the question as to the desirability of substituting 

 sodium citrate for ammonium citrate in the determination of reverted 

 phosphoric acid. The subject is simply brought forward at this 

 time in order that those chemists who are interested may give it 

 some thought. 



