The solubility of thioacetazone was measured in aqueous mixtures of deep eutectic solvents (DESs) with choline chloride as the hydrogen bond acceptor within the temperature range (298.15–313.15) K. The drug solubility in the neat DESs was found to be higher than that in water: by 53 times when malonic acid was used as the hydrogen bond donor, by 37 times with tartaric acid and by 33 times with citric acid in this role. The density of the water, neat DESs and their mixtures was determined at different temperatures. The density of the solvents under study was higher if the molecules of the acids contained in them had a bigger number of active functional groups. However, their solvating capacity was lower. The experimental data of the drug solubility in DES mixtures were shown to agree with the Hansen solubility parameters. The thermodynamic functions of thioacetazone dissolution were calculated and the intermolecular interactions in the systems with DESs were discussed.
