brought out more clearly in the next table, where the differences 

 are expressed percentagely, taking the absorption by the cal- 

 careous soil, at the close of each period, as 100. 



Percentage differences in the fixing power of five soils Jor soluble 



phosphates. 



From this presentation of the data, it is seen that the fixing 

 of soluble phosphates by the calcareous soil, during the first day, 

 exceeds that of the other four soils by as much as 33.18 to 46.99 

 per cent; at the end of 8 days its effect is in excess from 22.88 

 to 3 7. 41 per cent. ; while, at the close of the last period, it is still 

 in excess by as much as 5.81 to 26.58 per cent, 



It is to be noted that, even at the end of 26 days, not all of the 

 phosphate had been absorbed, although the quantity for the cal- 

 cerous soil, found in the solution, is recorded as a "trace." 



The unfortunate aspect of these observations, as indeed of all 

 which have been cited, is the very large amounts of phosphates 

 used in proportion to the soil. 



ABSORPTION BY SOILS OF SULPHURIC AND CITRIC ACIDS, AND 



CHLORINE. 



It seems to have been quite the universal opinion of the 

 earlier investigators along these lines that little or none of the 

 negative radicles are absorbed by soils, with the exception of 

 phosphoric and silicic acids. It is true, however, that sonue in- 

 dications of absorption of sulphuric acid and of chlorine have 

 been observed, but the tendency was to attribute them either to 

 errors of observation or else to the formation of ammonium 

 chloride or sulphate, in which cases (Voelcker's instances) they 

 were regarded as being lost on heating after evaporation. 



In our own experience, however, as will be given later, there 

 appears little question but that nitric acid and sulphuric acid, 



