. . . . "The hydro-active substance may be a water soluble salt like magnesium sulfate, magnesium chloride, potassium sulfate, sodium chloride, sorbitol, inositol, urea, or a saccharide such as glucose or fructose or dextran, or, a hydrophilic polymer such as a poly(hydroxyalkyl methacrylate) with a molecular weight of 30,000 to 5,000,000, poly(vinylpyrrolidone) with a molecular weight of 10,000 to 360,000" . . .