150 MOVEMENT OF SOLUBLE SALTS 



sodium carbonate as a dellocculating agent but less than 

 one-half as powerful as sodium nitrate. Percolation was 

 at the rate of 1.2 cc. per hour for soil containing 1886 parts 

 per million of sodium chloride and at the rate of 4.1 cc. 

 per hour for soil containing 11,457 parts per million of 

 sodium sulphate, while that of the untreated soil was at 

 the rate of 10.2 cc. per hour. Hare (8), however, found 

 sodium chloride much easier to leach into the deeper 

 layers of the soil than sodium sulphate and that the dif- 

 ference was many times greater in an adobe soil than in 

 a sandy loam. It was with great difficulty that the sodium 

 sulphate was leached downward in the adobe soil, the 

 depth being 2 inches for three six-inch irrigations, while 

 this amount of irrigation washed the sodium chloride to 

 a depth of 32 inches, and four three-inch irrigations washed 

 the sodium carbonate to a depth of 20 inches. The sodium 

 chloride moved more freely than the other two salts in 

 both adobe and sandy loam. 



The above experiments were performed with pure salts. 

 Cameron and Patten (3) found that when using black 

 alkali soils brought from the fields and containing notable 

 quantities of sodium sulphate, besides the sodium car- 

 bonate and small quantities of chlorides, the " neutral 

 salts such as the chlorides in the presence of carbonates 

 can be comparatively readily and completely leached 

 from the soil. With continued leaching of soils contain- 

 ing 'black alkali' there is an increase in the rate at which 

 percolation takes place, due probably to the reduction of 

 the amount of alkali present and its effect on the physical 

 structure of the soil. Soils containing 'black alkali' 

 can be reclaimed by leaching, but the time and the amount 

 of water required are probably much greater than in the 

 case of white alkali.'' 



