122 THE SOIL SOLUTION 



this case, it would be anticipated that the concentration of the 

 drainage water would increase as the amount of flow diminished 

 but the composition of the dissolved salts would remain prac- 

 tically constant until some one or more of the alkali salts was 

 completely removed. There are, unfortunately, but few experi- 

 mental data by which these can be tested. In the accompanying 

 table are given the results of an investigation on the reclamation 

 of an alkali tract near Salt Lake City, Utah, where observations 

 on the composition of the drainage water were made at fre- 

 quent intervals for more than three years. 1 



At first sight these results might appear to show that the com- 

 position of the salts was remaining reasonably constant. This 

 conclusion must be received with caution, however. Variations 

 do occur in the constituents which are present in smaller amount, 

 but the variations are not systematic and may plausibly be ex- 

 plained by dilution of saturated solution by unsaturated solu- 

 tion on entering the drains. Confining attention therefore to 

 the constituents occurring in larger proportions, namely, sodium 

 chloride, sodium sulphate and sodium bicarbonate (including 

 the normal carbonate) it should be remembered that the per- 

 centage of sodium in these three salts does not vary much, and 

 the "constancy" may be more apparent than real. Indeed a 

 close inspection of the results indicates that while the sodium 

 is remaining practically unchanged, there is some decrease in 

 the chlorine and a corresponding increase in the sulph-ion. From 

 this it would follow that the sodium chloride was being washed 

 out of the soil more rapidly, proportionately, than sodium sul- 

 phate; and it would also appear that the solution entering the 

 drains was not in final equilibrium with the salts in the soil. 



How long drainage must continue before there is a radical 

 change in the composition of the seepage water cannot be pre- 

 dicted, and unfortunately data regarding this point are not avail- 

 able. It is certain that in time some one or more of the salts 

 in the soil would be removed and the nature of the drainage 

 1 See, Calcium sulphate in aqueous solution, by Frank K. Cameron 

 and James M. Bell, Bull. No. 33, 1906, pp. 10 and 70, and Reclamation 

 of alkali land in Salt Lake Valley, Utah, by Clarence W. Dorsey, Bull 

 No. 43, 1907, p. 13, Bureau of Soils, U. S. Dept. Agriculture. 



