Solubility studies of silver sulfonamides

The solubilities of silver sulfapyridine, silver sulfamethazine, and silver sulfamethizole as a function of pH were determined in nitric acid-potassium nitrate, acetate, and sulfonic acid buffers. All silver sulfonamides showed an increase in solubility with increasing hydrogen-ion concentration, a behavior which closely paralleled the protonation of the p-amino function of the sulfonamide. A silver-ion selective electrode was used to measure silver-ion concentration in solution and the methods of known subtraction and known addition were used to measure total silver. Both silver sulfamethizole and silver sulfamethazine were ionized completely in solution. Silver sulfapyridine was ionized completely only in the more acidic pH 2-3 range. A comparison of the physical properties of the silver salts for which mortality studies were available revealed a unique set of properties for silver sulfadiazine.