64 DAVID R. BRIGGS 



range of pressures and at sufficiently low concentrations of solute to 

 make such an extrapolation dependable. Osmotic pressures as low 

 as, or even lower than, 10 mm. of water will often be necessary. At 

 such low pressures, surface tension differences between solvent and 

 solution, and their effects on the capillary rise of the liquids in the 

 capillary tubes that may be employed for creating the hydrostatic 

 head at equilibrium, must be taken accurately into account as must 

 also density differences between the solutions. The osmometer 

 should be so constructed that it can be held in a constant temperature 

 bath accurate to 0.02 to 0.01 °C. in order to eliminate as far as possible 

 fluctuations due to density changes and surface tension changes as 

 well as osmotic pressure changes with temperature. 



References 



GenernJ References 



1 . Lewis, G. N., and M. Randall Th''rinodynamics. McGraw-Hill, New 



York, 1923. 



2. Mark, H., Physical Chemistry of High Polymeric Systems (High Polymers, 



Vol. II). Interscience, New York, 1940, p 228. 



3. Wagner, R. H., "Determination of Osmotic Pressure," in Physical Methods 



of Organic Chemistry, 2nd ed., A. Weissberger, ed. Interscience, New 

 York, 1949, Chap. XI. 



4. Ferry, J. D., "Ultrafilter Membranes and Ultrafiltration," Chem. Revs., 



18, 373 (1936). 



5. Lifson, N., and M. B. Visscher, "Osmosis in Living Systems," Medical 



Physics, 0. Glasser, ed. Year Book Publishers, Chicago, 1944. p. 869. 



Theory 



6. Ostwald, W., Kolloid-Z., 49, 60 (1929). 



7. Flory, P. J., J. Chem. Phys., 10, 51 (1942). 



8. Huggins, M. L., /. Am. Chem. Soc, 64, 1712 (1942) ; /. Phys. Chem., 46, 



151 (1942); Ind. Eng. Chem., 35, 216 (1943). 



9. Scatchard, G., J. Am. Chem. Soc, 66, 2315 (1946). 



10. Adair, G. S., Proc. Roy. Sec. London, A109, 292 (1925); A120, 573 



(1928); A126, 16 (1929); J. Am. Chem. Soc, 51, 696 (1929). 



11 . Donnan, F. G., Chem. Revs., 1, 73 (1924). 



Methods and Techniques 



FREEZING POINT 



12. Adams, L. H., J. Am. Cfiem. Soc, 37, 481 (1915). 



