On the osmotic pressures of some concentrated aqueous solutions

Abstract

This communication gives an account of measurements of osmotic pressures of aqueous solutions of cane sugar, dextrose, galactose, and mannite. The method adopted is that briefly outlined by us in Vol. 73, ‘Roy. Soc. Proc.’ A gradually increasing pressure is placed upon the solution (which is separated from the solvent by a semi-permeable membrane) until the solvent, which at first flows into the solution, reverses its direction and is squeezed out. The pressure, when there is no movement of the solvent, is considered to be the osmotic pressure. Owing to the difficulty of determining the exact point at which no movement takes place and for other reasons, the experi­ments are carried out so as to enable an observation to be made of the rate of movement of the solvent, both when the pressure on the solution is just below and when just above the turning point pressure. The osmotic pressure is deduced from these rates. The range of pressures covered by the experiments is from 12 to 135 atmospheres.