Phase diagrams of aqueous solutions of the potassium salts of malonic, succinic, and glutaric acids

Abstract Phase equilibria in aqueous systems of 1:1 and 2:1 KOH and the following dicarboxylic acids have been studied: malonic, succinic, and glutaric. The temperature of thermal transitions was determined in solutions of known composition using Differential Scanning Calorimetry. The identity of the least soluble solid was determined by a combination of X-ray crystallography and infrared spectroscopy. Combining these data facilitated construction of a partial phase diagram for each system. In general, the potassium salts of carboxylic acids studied here are at least as soluble as their sodium salt analogs, and generally more soluble than the parent acids with some temperature dependent exceptions. While the single potassium salts readily formed in the respective systems studied here, we did not observe the formation of any of the double salts.