Nitriding phosphate glasses of variable sodium content, xNaO·(1−x)P2O5, in anhydrous ammonia gas is described. The thermal expansion coefficient and dissolution rate in water decrease with increasing P2O5 and nitrogen content The dilatometric softening point and glass transition temperature decrease with increasing P2O5 and increase with increasing nitrogen content. The water content of the as-melted glasses increases dramatically with increasing P2O5 content. The N 1s and O 1s spectra were determined with X-ray photoelectron spectroscopy.