EXPERIMENT STATION BULLETINS. 631 



tions does not change during the determination but the alkalinity of 

 alkaline solutions is decreased. With mixtures of pure calcium phos- 

 phates and calcium sulphate the reverse is true, i. e., acid and neutral 

 solutions become more alkaline while alkaline ones do not change. 



With citrate solutions ranging in reaction from Ph G.G to 7.8 the 

 magnitude of the variation in the results of the analysis of calcium 

 phosphate is usually small. There is however a distinct decrease in 

 the solubility of both di- and tricalcium phosphate with an increase in 

 alkalinity. 



Precipitated tricalcium phosphate is much more readily soluble in 

 ammonium citrate solution than is raw rock phosphate. 



There appears to be no good reason for changing the reagent which 

 has been prescribed for use but the official methods for preparing this 

 solution should be replaced by more accurate ones. 



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