336 STATE BOARD OF AGRICULTURE. 



KOH treatments were much smaller in magnitude than the solubility factor 

 of calcium as Ca(0H)2 and magnesium was not found in sufficient quantities 

 in any of the extracts from either the KOH or Ca(0H)2 treatments to alter 

 the above conclusion. Providing Ca(0H)2 was formed by the KOH treat- 

 ments the presence of a greater quantity of calcium should be expected in 

 the extracts. On the other hand potassium fixed from KOH was apparently 

 liberated by the Ca(0H)2 treatments. The solubilities of the hydroxides 

 in question is probably a most important consideration. Potassium fixed 

 from KOH was liberated again by treating with CaCl2. 



In summarizing the effects of hydrolyzing or molecular dissociating salts 

 attention must be given to the different classes involved. In case of the 

 KC2H3O2 treatments there was evidence of exchange between the potassium 

 of the salt and calcium And magnesium of the soils thereby agreeing in this 

 respect with results from the neutral salt treatments. Much greater quan- 

 tities of potassium were fixed, however, and the extracts were over balanced 

 with C2H3O2 ions as shown by the titrations with 0.1 N KOH solution. The 

 acetate acted similarly to a neutral salt and hydroxide combined giving 

 uncombined C2H3O2 ions in the soil solutions, but the uncombined C2H3O2 ions 

 were not a measure of the quantity of potassium fixed by the soils. Effects 

 produced by Ca(C2H302)2 were probably similar to those obtained by the 

 KC2H3O2 treatments. K3PO4 may be considered representative of another 

 class of hydrolyzing salts, both members of which were fixed by the soils. 

 As shown by lack of chemical equivalents in the case studied, different soil 

 factors were probably responsible for the fixation of potassium in PO4 ions. 

 It was apparent, however, that these factors were closely related to the cal- 

 cium and magnesium content of the soils. Either calcium and magnesium 

 were responsible or some other factor or factors closely allied with these 

 elements, because in nearly all cases the alkaline soils fixed a greater cjuantity 

 of K3PO4 than the acid soils of the same class. Some soils fixed a greater 

 equivalent of potassium ion than P04-ion, and in the other soils this order 

 was reversed. Whether the potassium ion or P04-ion is fixed in greater 

 quantity seems to depend upon the quantity relationships of the soil factors 

 involved. Effects of Ca(H>P04)2 and K2C'204 were similar to those of K3 

 POi, except magnesium was present in extracts from the K2C2O4 treatments, 

 although the quantity was not determined, and this element was probably 

 in the form of MgC204. Although undetermined, these reactions are prob- 

 ably reversible because reactions between neutral salts and soils and KOH 

 and soils are reversible at least with respect to their basic ions. FeCls 

 belongs to a third class of hydrolyzing salts being acid in reaction. From 

 effects of this salt upon the soils it is believed that the iron was precipi- 

 tated in the soil mass as the hydroxide and that the reaction is not revers- 

 ible. In general the effect of this salt upon the soils compared to the effects 

 produced by treating the soils with HCl. 



From the results of this investigation it is believed that only small quan- 

 tities, if any, of potassium, sodium, iron or aluminum were present in the soils 

 used in an exchangeable condition. Tliis jjoint was discussed more fully 

 in connection with the summary of the experiments with soils and neutral 

 salts. 



Data presented favor the conclusion that the reaction between soils and 

 the chemical compounds used is chemical in nature rather than physical. 

 The main lines of evidence bearing on this point have already been discussed, 

 and they are principally the relationships shown between fixation and the 

 calcium and magnesium of the soils or other elements fixed in the soils by 



