158 AGRICULTURAL ANALYSIS 



60 grams of molybdenum trioxid in a liter, while the Pem- 

 berton solution contains 66 grams. There is, therefore, 

 not much difference in strength. The absence of nitric acid, how- 

 ever, from the Pemberton solution favors the deposition of the 

 molybdic acid when heat is applied. 



Kilgore, therefore, conducts the analysis as follows: The 

 solution of the sample is made according to the official nitric and 

 hydrochloric acid method for total phosphoric acid. For the 

 determination, 20 to 40 cubic centimeters are used corresponding 

 to two-tenths or four-tenths gram of the sample. Am- 

 monia is added until a slight precipitate is produced and the 

 volume is then made up, with water, to 75 cubic centi- 

 meters. Add some ammonium nitrate solution, from 10 to 15 

 cubic centimeters, but this addition is not necessary unless 

 much of the nitric acid has been driven off during solution. Heat 

 in the water bath to 60 and precipitate with some freshly filtered 

 official molybdate solution. Allow to stand for five minutes, filter 

 as quickly as possible, wash four times by decantation, using from 

 50 to 75 cubic centimeters of water each time, and then wash 

 on a filter until all acid is removed. The solution and titra- 

 tion of the yellow precipitate are accomplished as in the Pem- 

 berton method. The agreement of the results obtained by this- 

 modified method was much closer with the official gravimetric 

 method than those obtained by the Pemberton process. 



142. Investigations of the Volumetric Method by the Asso- 

 ciation of Official Agricultural Chemists. The great value of the 

 volumetric method by reason of the saving of time in analytical 

 work, especially where great numbers of analyses are to be made, 

 led to a painstaking investigation of its reliability and agreement 

 with the gravimetric process on the part of the official chemists. 

 The results of these investigations are published in detail in the 

 proceedings of the association. 10 



19 Division of Chemistry, Bulletin 47, 1896 : 70. 

 Division of Chemistry, Bulletin 49, 1897 : 60. 

 Division of Chemistry, Bulletin 51, 1898 147. 

 Division of Chemistry, Bulletin 56, 1899 : 36. 

 Division of Chemistry, Bulletin 57, 1899 : 69. 

 Division of Chemistry, Bulletin 62, 1901 : 35. 

 Bureau of Chemistry, Bulletin 67, 1902 : 22. 

 Bureau of Chemistry, Bulletin 8r, 1904 : 164. 



