Glass formation region in the Ho203-Al203-Si02 system extended from 9 to 30 mol% Ho203. The chemical durability of these glasses was measured in simulated physiological solutions to determine their usefulness for in-vivo radiotherapeutic applications. The dissolution rates of glass plates were barely measurable in distilled water at 37 or 70 deg C being no more than 4x10-9g/cm2min. Analysis of the test solutions and glass surfaces showed that little if any holmium leached from glass plates or microspheres into distilled water or saline solutions at 37 or 70 deg C. The dissolution rates of these glasses in 0.1N HCl increased with temperature and with the substitution of Ho203 for Al203 or Si02. The density, refractive index, thermal expansionand Vickers hardness increased with Ho203 content.
