This study is aimed at comparing chemical durability with structure of phosphate glasses differing in composition. The durability was checked by the treatment of these glasses in alkaline salt melts in the range 350-540 deg C for 24/h. No essential difference was found in the influence of the anion composition of the salt melts used on glass durability. The most critical factor was the temperature of the treatment & glass composition. A parameter called the General Glass Composition (GGC) & reflecting the total amount of valences of all metal modifier ions per one valence of a phosphorus ion was introduced to systemise these glasses to the character of their network structure. It was found that chemical durability of the glasses increased with the growth of GGF. In the simplest cases, GGC equal to 1, 2 & 3 corresponds to meta-, pyro-, & orthophosphate compositions. respectively.
