A copper phosphate water soluble glass composition. The composition of the glass may be adjusted so as to release copper at a uniform preselected rate and to produce a desired pH in the resultant solution. In one application of the glass copper may be supplied to an animal from an implant formed from a cupric oxide/phosphorus pentoxide glass which also incorporates one or more glass modifying oxides such as alkali metal oxides and alumina, to control the glass solubility. Suitable glasses comprise 5-55 mole % cupric oxide + alkali metal oxides. 45-75 mole % phosphorus pentoxide, and not more than 15 mole % alumina, where the copper oxide concentration is not less than 5 mole %.