Oct. 14, 1918 Fertilizer Potash Residues in Hagerstown Silty Loam 69 



thus extracted a second time, with a recovery (net) of 0.00190 per cent 

 of potash in the second extract. 



It happens that the quantity of potash removed by the two extrac- 

 tions of the soil from plot 4 was practically the same as the amount 

 removed by a single extraction with ammonium-chlorid solution of 

 normal concentration. 



Summary of fine-soil potash solubilities 



Treatment of potash. 



In terms of air-dry fine 

 soil. 



In terms of total 

 potash. 



Plot. 



Total 



Soluble in hot (1.115 sp. gr.) hydrochloric 



acid, 10 hours, 1:10 



Soluble in warm (40° C.) NI5 hydrochloric 



acid, 5 hours, i :io 



Soluble in distilled water: 



Flask method, 5 hours 40° C, 1:10 



Flask method, highest results 



Percolation method, 21° C, 1:10, 4 to 6 



days 



In water from clay washing 



Soluble in carbonated water by percolation, 



21° C, I :io, 2 to 5 days 



Soluble in Nj^ ammonium-chlorid solution, 

 5 hours, 40° C, 1:10: 



First extraction 



Second extraction 



Per cent. 

 3.821 



.3687 



.0143 



.0032 

 . 0046 



.0045 

 .0038 



. 0076 



0094 

 0020 



Per cent. 



543 



4072 



0301 



0049 

 0075 



0080 

 0087 



0140 



0187 

 0021 



Per ce7it. 

 ICO. 000 



649 



374 



084 

 120 



118 

 099 



199 



246 

 052 



Per cent. 

 100. 000 



11-493 



.850 

 .138 



. 212 



. 226 

 . 246 



•395 



.528 

 •059 



In general, only about one-tenth of the potash of these soils can be 

 extracted from the fine soil in its natural state of subdivision by strong, 

 hot hydrochloric acid acting at the temperature of boiling water for a 

 period of 10 hours, when 10 cc. of the acid are used for each gram of 

 the soil. 



When the conditions of solution are closely maintained, the potash 

 of the potash-fertilized plot is almost one-fifth more soluble in strong, 

 hot acid than that from the untreated plot. 



When mild solvents are used to extract the potash, the differences in 

 the condition of this element in the two soils are much more pronounced. 

 The solubility of the potash in the potash-fertilized plot is from 1.5 to 

 2.5 times greater than in the untreated plot. 



The similarity of the ratios between the percentages of potash dissolved 

 from the two soils by the respective mild solvents, distinctly suggests 

 identity in the nature of the materials acted upon in the soils by these 

 solvents. On assuming that water and its solutions of carbon dioxid 

 and of ammonium chlorid act only upon those potassium compounds of 

 the soil that weak hydrochlorid acid can attack, and expressing the 



