ELISHA MITCHELL SCIENTIFIC SOCIETY. 119 



Four of these portions, representing each of the above soils, 

 were analyzed immediately after mixing, four were analyzed two 

 days after, four three days after, one week after, and so on. At 

 the end of every week the contents of each of the vessels were 

 stirred, and again moistened if at all dry. 



In analyzing, the whole mixture, consisting of 5 grams, was 

 treated with water and washed till no longer acid for the deter- 

 mination of phosphoric acid, then digested with lOOce. neutral 

 ammonium citrate (S. G.=1.09) for 30 minutes at a temperature 

 of 65° C. ; and continuing according to the Association Method, 

 referred to above, for the insoluble phosphoric acid, with some 

 slight modification made necessary by the larger bulk of the 

 materials. The total phosphoric acid of course remains the same 

 throughout. 



Allowing -| of the acid phosphate to be soluble phosphoric acid, 

 we see that the ratio the soluble phosphoric acid bore to the soil was 

 in the experiments, 1 to 32; i. e., for every part of the soluble 

 phosphoric acid in the mixture there existed 32 parts of the soil ; 

 a mixture more nearly representing nature than is recorded in 

 the experiments of Wagner, where the rati') was 1 : 3 and 1:12. 



(In the table (Table VI) the corrected percentages of insolu- 

 ble phosphoric acid are given, which were obtained by subtracting 

 from the insoluble phosphoric acid found in the mixture the 

 per cent, of phosphoric acid previously found in the different 

 soils. 



9 



