New York AGRICULTURAL EXPERIMENT STATION. 271 
The curves of Fig. 18 express results obtained with four initial 
concentrations of hydrochloric acid, as given on p. 277, Table VIII, 
column 3. Similar curves are obtained by plotting the results tabu- 
lated for the other acids. The forms of the curves (compare with 
Figs. 16 and 17) show clearly that the reaction has the character- 
istics noted above for adsorption and does not fulfil the requirements 
of the formation of a hydrolyzible salt. 
This fact is brought out even more strikingly by the application 
of Ostwald’s graphic criterion for adsorption. According to this 
if, using equilibrium data, one plots dilutions of the solution as 
ordinates and amounts of solute adsorbed as abscissae, the char- 
acteristic curve for adsorption is similar to a hyperbola. In 
the case of formation of a hydrolyzible salt of the kind in question, 
the curve would be very different. For the combination of any 
acid at all, the dilution could not exceed that corresponding to the 
concentration constant. Nor, until the base is completely neutral- 
ized, can acid in contact with it at equilibrium be of less dilution 
than the constant, since the acid will continue to combine until that 
dilution is reached. Consequently, as more acid is added to a 
solution in contact with the base, the latter takes it up, keeping the 
dilution constant until the basic valences are all saturated, the curve 
expressing these conditions being a horizontal line. Further addi- 
tion of acid simply decreases the dilution, since further combination 
is impossible, and the curve drops perpendicularly. The two types 
of curves are illustrated in Fig. 19. Curves 1 and 2 represent ac- 
. . ° Pits : 
sorptions following the equation B=“, in which p has the values 
C2 
T and 2 respectively. In the former case the curve is a true 
hyperbola. In the latter it represents the average relations observed 
by Freundlich in adsorption by charcoal. The rectilinear curve 3 
represents the conditions in the formation of a solid salt, as de- 
scribed above. In Tig. 20 the results experimentally obtained with 
the various acids are graphically represented. Comparison with 
Fig. 19 shows that the reactions represented are adsorptions, 
