570 STATE BOARD OF AGRICULTURE. 



It is evideut from the above table that common salts of verv high 

 solubility do occur in the alkali soils. 



Now if it has been proved absolutely that the salts in tlie above table 

 do occur in the soils of the arid region, then there is no reason whatever 

 why they should not occur also in the humid regions, but only in very 

 small quantities of course. The only chief and important difference be- 

 tween the humid and arid regions is climatic, the chemical composition 

 of the soils of both regions does not var}- so greatly. In the humid 

 regions there are few cases known where seemingly alkali conditions 

 exist. The composition of the salts which form the alkali conditions con- 

 sists in some of the cases reported (8) of NaKO., KNO,, Mg(N03), 

 CaCNO,),, CaSO,, CaCl,, CalHCO.),, MgCHCOg)., Na,SO„"etc. 



That salts of high solubility may exist in the soil solution is further 

 confirmed by the reaction that is conceived to take place betv/een the 

 soil and a soluble salt added. Thus, Al^^ Fe^^, Mgx, ^\, CaCSiOg)^^, 

 (H20),,+2KC1 = A1,, Fe,, Mg^, Na^, K2(Si03)'^(H20),+CaCl2. The CaCP 

 is assumed to be in solution. 



The evidences, therefore, of the existence of salts of high solubility 

 in the soil solution are overwhelmingly strong. 



The solubility of some of the salts which are likely to occur in the 

 soil solution Avas presented in the original report. For convenience and 

 immediate usefulness they are repeated herewith : 



Table 7. Solubility of Various Salts at about 20°C. 



It is verv evideut that the solubilitv of most of the salts in the list 

 is very high. 



Since the formation of these salts is comparatively slow, and their 

 accumulation to any appreciable extent is prevented by the excessive and 

 frequent rains in the humid regions, their amount in the soil solution is 

 relatively small and does not form a saturated solution, probably not 

 even at a low moisture content. Those salts, of course, that form a 

 saturated solution are separated in the solid phase. At the high mois- 

 ture content, therefore, these salts are diluted and cause only a small 

 lowering of the freezing point but as the water content is reduced they 

 become more concentrated and they produce a correspondingly greater 

 lowering of the freezing point. That is exactly what the experimental 



(8) See original report loc. cit. 



