experijMknt station bullp:tins. 



(iOl 



TABLE 7.— RATK AM) KX'JKNT OF SOLUBILITY OP SAND TREATKI* wmi SALTS 

 AND THKN WASHED UNTIL ALIy PHEK SOLUBLE SALTS WERE ELIMINATED. RATIO 

 OF SOIL TO WATER WAS ABOUT 1 TO .7 AND MIXTURE MAINTAINED AT ROOM 

 TEMPERATURE. FIGURES REPRESENT FREEZING POINT DEPRESSION. 



The above data reveal many exceedingly interesting and very im- 

 portant and fundamental facts regarding the rate and extent of solu- 

 bility of soils treated with various single salts and then washed, until 

 all their free soluble salts were eliminated. In the first place it is imme- 

 diately seen that the rate of solubility of all the soils with all the various 

 single salts is very slow or that e(iuilibrium is not attained very rapidly. 

 The amount of material going into solution each day is slight and the 

 process continues for a long time, even 120 days in some cases, but as a 

 rule it tends to attain an apparent constancy at the end of about GO 

 days. The rate of solubility is not directly proportional to tlie time ele- 

 ment, Imt tends to increase, on the whole, rather slowly and gradually* 

 witli the time element, up to about 40 or GO days, and then becomes more 

 or less stationary or progresses very slightly thereafter. During the 

 first four or five days the velocity of solubility appears to be slightly 

 greater than at the succeeding days but the difference is very small 

 except in a few cases. With the exception of the (NHj).S04 treatments, 

 the amount of material going into solution at the very beginning of the 

 experiment does not exceed 200 parts per million of solution or .008 °C 

 depression, per day. The soils treated with (NH4)oS04 show the great- 

 est velocity of solubility followed l)v NaNO.,, NaC.H./).,, KNO,, KCl, 

 rCSOs MgSO^, Ca(NO,)„ KH.,PO, and CaH/(POJ,. The order of the 

 hist nine salts is not alwaj's exactly the same, but there is a general 

 tendency towards that order. The interesting fact to be noted is that 

 the rate of solubility of nearly all the soils treated with CafNO.)., 

 KHpPO^, and CaH4(P04).> is about the same as that of the untreated 

 soils or checks. These three salts, therefore, and especially the CaHj- 

 (PO^), did not increase the rate of solubility of soils as did the other 

 salts. The greater velocity of solubility of the soils treated with the 

 (NH4)oS04 is only of short duration. 



