6 
Walter Stiles 
temperature and osmotic pressure at constant concentration in the 
case of sucrose. These curves are constructed from the figures pro¬ 
vided by Morse and his co-workers. For a large mass of further data 
reference may be made to the original papers of these workers. 
It will be observed that in concentrations up to normal the pro¬ 
portionality between concentration and osmotic pressure holds quite 
well, but it is to be noticed that the measured osmotic pressure is 
always higher than that calculated from the gas law. This difference 
Fig. 6. Relation between concentration and osmotic pressure of solutions of 
sucrose and glucose. I. Sucrose at o°C. II. Glucose at o°C. III. Theoretical 
curve at o° C. (Data from Berkeley and Hartley.) 
between observed and calculated values is greatest at the higher 
concentrations, and in very high concentrations this divergence 
increases, as the curves in Fig. 6, constructed from the data obtained 
by Berkeley and Hartley, clearly show. The relation between tem¬ 
perature and osmotic pressure is also not one of strict proportionality 
over large temperature intervals. It has been pointed out by Morse 
that the divergence between observed and calculated values is con¬ 
siderably lessened even at high concentrations if it is assumed that 
the osmotic pressure is equal to the pressure the solute would exert 
