The Cryoscopic Method for the Determination of "Bound Water"

Abstract

In 1922 Newton and Gortner (1) put forward the hypothesis that at least a portion of the water associated with the hydrophilic colloids in plant tissues was in a "bound" form, in which form it exhibited physicochemical properties which would serve to differentiate it from the "free" water of the vacuolar sap. It was suggested that bound water might be unavailable for the solution of sucrose and accordingly a method for the estimation of such bound water was proposed which consisted essentially in first determining the freezing point of the solution which contained the hydrophilic colloid and denoting this value as A. An amount of the sol was then taken which contained exactly 10 gin. of total water. To this portion there was added 0.01 mole of sucrose and a second depression of the freezing point, designated Aa, was determined. If all of the 10 gin. of water were free to dissolve sucrose ha should differ from A by the freezing point depression of a molar solution of sucrose which according to Satchard (2) should be 2.085 °, corresponding to a gram molecule of sucrose-hexahydrate dissolved in 892 gm. of water.The formula which Newton and Gortner proposed Aa --(Zx -b Kin) percentage of bound water ---X 89.2 (1) Aa --A was tested by them on aqueous solutions of gum acacia and on certain plant saps and appreciable amounts of bound water were apparently demonstrated to be present. This method has been extensively used by numerous plant physiologists-especially Newton and his coworkers (3-6)--and has

The hydration of gum arabic and glycogen

“…Gortner & Gortner [1934] obtained values of 0 6-0-7 for the hydration of calcium gum by the cryoscopic method and Gortner's earlier work indicated an amount greater than 1 so that the figures of these authors are in reasonable agreement with my own figures.…”

Nature of Bound Water in Colloidal Systems

“…It has beeni suggested (17) that bound water is due to the orientation of water molecules about the colloidal particles and that the water, thus removed from the body of the solution, loses its solvent properties. A few investigators have disagreed with these premises.…”

Water structure theory and some implications for drug design

“…In the 1930s Gortner and co-workers carried out experiments dissolving sucrose into water in various environments and determining how much had dissolved by measuring lowering of the freezing point (Gortner & Gortner 1934). They found that bound water, for example cell water, dissolved less sucrose than free water did and hence inferred that water in these situations was more structured than the bulk.…”