EXPERIMENT STATION BULLETINS. 597 



MgSO^ solution varies from about 55% in the case of some clays to about 

 100% in the case of the artificial substances. On the whole, however, 

 the percentage of the original concentration that was imparted to the 

 solution of the various agricultural soils is quite high. 



The NaCjHsO, solution increased the strength of the solution of the 

 different soils to a high degree. In the case of the more artificial sub- 

 stances, quartz sand, kaolin, etc., the increase amounts to about 100% 

 and in the agricultural soils it lies between 70 and 90%, with few ex- 

 ceptions. 



Of all the salts used the phosphates increased the concentration of the 

 soil solution of the agricultural soils to the last degree. Indeed it will 

 be seen that, with the exception of the artificial substances, the strength 

 of the soil solution of all the agricultural soils is increased in most cases 

 to only about 10%. Hence, the acid phosphate salts produced entirely 

 different results from the neutral salts. 



This part of the main investigation, therefore confirms the previous re- 

 sults and conclusions, and goes to show that the different compounds em- 

 ployed have an entirely different effect upon the concentration of the solu- 

 tion of the various soils. In the case of the neutral salts the solution of the 

 agricultural soils was increased from 35 to 100% of their added strength, 

 while in the case of the acid phosphate salts only a very small portion if 

 any of their concentration was added to the soil solution, amounting in 

 the majority of cases to only 10%. All the salts including the phos- 

 phates, behaved the same in regard to the artificial substances, the quartz 

 sand, kaolin, burned soils, etc., as they all increased the concentration of 

 their solution to about the same degree, 100%. The neutral salt solu- 

 tions did not behave uniformly in the different types of soils; some of 

 the salts produced the greatest increase in concentration in the sands 

 and the smallest in the clays, while other salts caused about the same 

 degree of concentration in all the distinct types of soil. 



The results obtained with the burned soils are of great interest and 

 need special emphasis. These soils are the same as soils No. 1, 2, 3, and 

 4 in Table 12. They were burned to red heat in a muffle furnace. An 

 examination of the results obtained from these soils shows that after 

 burning they acted almost like quartz sand as the concentration of their 

 solution was increased to almost 100% by all the salt solutions except 

 the acid phosphates, while before burning such was not the case. 



The question now is, how is the increase in concentration of the soil 

 solution by the soluble salts brought about; and, what is the composi- 

 tion of the resulting solution? Before attempting to answer this ques- 

 tion one more phase of the investigation should be considered. 



EFFECT OF THE APPLICATION OF ACIDS UPON THE CONCENTRATION OF THE 



SOIL SOLUTION IN THE SOIL. 



In conjunction with the foregoing studies just considered the effect of 

 application of acids upon the concentration of the solution in the soil 

 was also studied. The procedure of experimentation was the same as 

 above. The acids employed consisted of HCl, HNO., n.i^O,, CM.X),, 

 C.^HgO-, and HCsHoO, in n/10 strength. There were only 13 soils used. 

 The results obtained are shown in Table 13. 



