620 STATE BOARD OF AGRICULTURE. 



Theoretically, Solution C should have a ratio of 1 : 3.765 and accord- 

 ing to the results of Hand (25) and of Patten and Marti (41) a somewhat 

 larger content of ammonia and of citric acid for the specified density. 

 According to Hand the sum of these two constituents should amount to 

 213.06 g. per liter, while Patten and Marti found 213.33 g. per liter 

 instead of 215.35. This is an agreement of one per cent which is prob- 

 ably as close as most solutions made for this purpose would check. 



A committee appointed for the purpose of investigating this matter 

 by the Division of Fertilizer Chemists of the American Chemical Society 

 (1) prepared and analyzed three supposedly neutral solutions. Their 

 results are expressed in grams of "Crystallized" critic acid per liter and 

 their recommendation reads, "Standard ammonium citrate solution shall 

 contain 186 g. crystallized citric acid and 43.7 g. ammonia per liter, 

 measured, at 20°," etc. This has been interpreted by subsequent critics 

 as referring to the anhydrous citric acid in which case the ratio of 

 ammonia to citric acid would be 1 :4.256. Such a solution would, in 

 the light of the above results be extremely acid. When it is considered 

 however that "crystalized" citric acid contains one molecule of water 

 of crystallization and the above figures are altered to conform to those 

 of other investigators the amount specified for use becomes 170.9 g. and 

 the ratio NH3 : C„HsO-, 1 : 3.911. Even this is of course too high and 

 would give an acid solution with a Ph somewhat below that of Solu- 

 tion "A." 



III. THE KELATION BETWEEN THE REACTION OF THE REA- 

 GENT AND ITS SOLVENT ACTION ON CALCIUM 



PHOSPHATES. 



In commercial fertilizers: The difficulty in preparing a reagent of 

 constant reaction early led to a consideration on the part of investi- 

 gators of the results of variations in this factor upon the analytical re- 

 sults. 



Thus Antz and Erlenmeyer (2) claimed that an acid citrate solution 

 dissolved the tricalcium salt more readily than did the neutral solution. 

 They also claimed that the treatment of the salt i. e., wliother it had been 

 dried at a high or low temperature, altered its solubility. 



Barille (5) found the same to be true when a neutral solution was 

 used and showed that a very appreciable amount of tricalcium phos- 

 phate was dissolved by such a solution. 



Dirks and Werenskiold (35) analyzed several samples of phosphatic 

 material using a neutral solution, three solutions of varying degrees 

 of alkalinit}', Herzfeld and Feuerlein's (26) solution (also supposedly 

 a neutral one but prepared in a particular way) and Wagner's acid 

 solution. The last proved to be incomparable with the others. None of 

 the alkaline solutions gave a clean separation between the two calcium 

 phosphates involved. They found that the neutral solution dissolved 

 the tricalcium salt appreciably but that its solubility decreased with 

 an increase in alkalinity. Beyond a certain point in this direction, 



