2O4 AGRICULTURAL ANALYSIS 



A full statement of the problem is given in the first part of the 

 report. In the second part the sources of error are discussed, 

 together with the precautions to be observed in order that these 

 errors may be avoided. In the third part are given the methods 

 of procedure which in the opinion of the committee give the most 

 acceptable results. 



These conclusions show : 



1. That the use of molybdic acid in separating the dissolved 

 phosphate is generally unnecessary. 



2. The phosphate soluble in the citric acid employed should be 

 precipitated immediately after its preparation. 



3. The precipitation should be accomplished by the iron-citrate- 

 magnesia mixture to be described. 



4. The iron-citrate-magnesia mixture should be added with 

 constant stirring. 



5. The shaker should have a speed of from 250 to 300 revolu- 

 tions or vibrations a minute. 



6. The temperature of the mixture should not go above 18. 



If the above rules are followed results are obtained which cor- 

 respond with those secured by other exact methods. Even slags 

 which have an exceptional content of silicic acid can be examined 

 by this method with certainty in the results. It may be considered, 

 therefore, that all the difficulties have been removed, and that a 

 simple method of precipitation which, upon the whole, is much 

 more reliable than those formerly employed, can be applied to the 

 examination of basic phosphatic slags. The solutions employed 

 are as follows : 



First. Concentrated Citric Acid Solution, 10 Per Cent. Exact- 

 ly one kilogram of chemically pure crystallized uneffloresced 

 citric acid is dissolved in water, diluted to 10 liters, and for the 

 purpose of preventing the growth of mould and other decom- 

 position products, five grams of salicylic acid are dissolved in the 

 mixture. 



Second. Dilute Citric Acid Solution, Two Per Cent. Exactly 

 one volume of the concentrated citric acid solution, above men- 

 tioned, is diluted with four volumes of water. 



Third. Molybdic Solution. One hundred and fifty grams of 



