ELISIIA MITCIiELT. SCIENTIFIC SOCIETY. 



9 



cannot speak definitely. However that may be, there seeni.s to 

 be not much doubt tliat the disparity will be greater or less 

 according to various conditions not well understood, and may 

 vary from a third or a half of a per cent, to even as much as 

 one per cent. ' 



Six feitilizers containing cotton seed meal were chosen. They 

 were not laboratory mixtures, l)ut bona fide commercial fertilizers 

 on sale in North Carolina. They will be distinguished as 56, 

 76, 77, 78, 110 and 57. In each the phosphoric acid was deter- 

 mined by dissolving two grams in nitric acid plus a little hydro- 

 chloric acid with protracted heating. This is designated in the 

 table below as ''acid sohition." Then in each the phosphoric 

 acid was determined by incinerating two grams and dissolving 

 the ash in nitric acid. This is designated in the table as 

 " incineration. '^ Following are the results: 



No. 57 was an old cotton seed meal fertilizer that had been 

 carried over from last season. The meal had completely changed 

 color to a dark brown, so that to the eye the fertilizer would 

 I sever have been judged to be a cotton seed fertilizer. In this 

 one alone was there no difference in the results of the two 

 methods. 



It is believed that the disparity in all these cases is probably 

 not so great as it should be; that is to say, that the incineration 

 method as here used probably does not give the full content of 

 phosphoric acid, for this reason. The inferiority of the solvent 

 power of nitric acid for phosphates to that of hydrochloric acid 

 is well rec()2:nized. I believe that this inferioritv is greater when 

 the phosj)hate has been ignited. To test this an acid phosphate 



