This is the third volume in the series on the chemistry and physical chemistry of milk constituents. Volumes 1 and 2 dealt with the commercially important constituents proteins and lipids, respectively. Although the constituents dealt with in this volume are of less commercial importance, they are, nevertheless, of major significance in the chemical, physical, technological, nutritional and physiological properties of milk and milk products. The constituents of milk dealt with in this volume are lactose, water, milk salts and vitamins. The chemical and enzymatic modification of lactose and the physico-chemical properties of milk are also discussed.