Oct. so. 1923 Soil Reaction in Relation to Calcium Adsorption 
107 
In the presence of KC 1 corresponding amounts of Ca(OH) 2 produced 
a smaller decrease in the hydrogen-ion concentration, indicating that the 
solubility and the ionization of the acid-forming substance in fuller's 
earth are increased by KC 1 ; in other words, there are more hydrogen 
ions to be neutralized by the hydroxyl ions from Ca(OH) 2 . On the other 
hand, in the presence of KC 1 calcium adsorption was entirely inhibited 
when small amounts of Ca(OH) 2 were added, and greatly reduced with 
the larger amounts. The adsorption of considerable quantities of cal¬ 
cium when the larger amounts of Ca(OH) 2 were added shows that the 
tendency of the calcium ions to combine with the radical of the acid¬ 
forming substance was not prevented by a large excess of K ions. One 
hundred cc. of a 0.5N solution of KC 1 contain nearly 2,000 mgm. of 
potassium, and yet adsorption of calcium took place when from 20 to 60 
mgm. were added in the form of Ca(OH) 2 . The net result of the presence 
of KC 1 was a greater hydrogen-ion concentration and larger amount of 
unadsorbed calcium. If the acid-forming substance produces a silicic acid 
the following ions are present: 
KC 1 ^K + + C 1 - 
Ca(OH) 2 ^Ca + + 2 OH“ 
H 2 Si 0 2 ^2 H+SiOg 
HOH ^H + +OH- 
If this represents the ionic condition, the neutralization is due to the 
hydroxyl ions from Ca(OH) 2 combining with the hydrogen ions of the 
acid-forming substance. From this standpoint the reaction can be con¬ 
sidered purely chemical. The potassium ions combine with the radicals 
of the acid-forming substance, producing a potassium compound. In 
the absence of KC 1 , as in Experiment 13, or when large amounts of cal¬ 
cium are added, as in this experiment, calcium ions combine with the 
radicals of the acid-forming substance. Larger amounts of calcium com¬ 
bine in the absence of KC 1 , and the ratio between the amount which 
combines and the amount added accords with the law of adsorption. 
GROUP D.—COMPARISON OF VARIOUS SOILS IN RESPECT TO THE INFLU¬ 
ENCE OF CALCIUM CARBONATE, CALCIUM HYDROXID, AND POTASSIUM 
CHLORID UPON THE P H , THE ADSORPTIVE POWER OF SOIL FOR CALCIUM 
FROM CALCIUM HYDROXID, AND THE CALCIUM SOLUBLE IN HYDRO¬ 
CHLORIC ACID AND POTASSIUM CHLORID SOLUTIONS 
EXPERIMENT 19.—COMPARATIVE POWER OP FOUR SOILS TO ADSORB CAIXIUM FROM 
CADCIUM HYDROXID 
The purpose of this experiment was to compare the calcium-adsorptive 
power of four soils. Neosho silt loam, Bates very fine sandy loam, 
Oswego silt loam, and Bates loam were used. Eight different solutions 
of Ca(OH) 2 were made and added to soil in different definite amounts. 
After the usual treatment, the unadsorbed calcium and also the P H values 
were determined on the extracts. The data obtained based on 10 gm. 
of soil are given in Table XIX. 
The Bates loam, a neutral soil, and Oswego silt loam, a moderately 
acid soil, both containing larger amounts of clay than the other two, 
adsorbed nearly the same amount of calcium. Neosho silt loam, less 
acid than Oswego silt loam, adsorbed the least. The outstanding physical 
property of this soil is its small amount of clay and large amount of silt. 
