38 
BULLETIN 1452, U. S. DEPARTMENT OF AGRICULTURE 
It is apparent that variations in properties of the different colloids 
correspond fairly closely to variations in the exchangeable bases and 
to variations in the at r\ it? — cT ra ^^°- The degree °^ correspond- 
ence between chemical composition and properties shown by these 
seven colloids is evidently not exceptional, inasmuch as many other 
colloids have been tested for single properties, and similar degree of 
correlation obtains between these single properties and chemical 
composition. 
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Fig. 2. — Relation between the heat of wetting and the a1.>0- + Fe»0 ~ ratio of soil colloid* 
Figures 2, 3, and 4 show how the heat of wetting, ammonia ad- 
sorbed and malachite green adsorbed vary with the 41 c\ _l"Fp O 
ratio in the case of 22 to 32 different soil colloids. The data utilized 
in these curves were taken largely from previous publications (#, 
90,47). 
These larger numbers of colloids show about the same order of 
correspondence between properties and silica ratio as the seven col- 
loids in Table 20. A few colloids in each figure deviate considerably 
more than the others from the average relation between silica ratio 
and property. However, the colloids which deviate from the aver- 
age relation in one property may conform to the average in another. 
