The solubility data of 5-amino salicylic acid in methanol, ethanol, carbon tetrachloride, and tetrahydrofuran (THF) at various temperatures were measured by gravimetrical method from (293.15 to 313.15) K under atmospheric pressure, and the solubility data were correlated as a function of temperature. The order of solubility is THF > carbon tetrachloride > ethanol > methanol. Further, some thermodynamic parameters such as enthalpy, Gibb’s energy, and entropy have also been evaluated for the dissolution process. It is observed that enthalpy and entropy are positive, whereas the Gibb’s energy of activation is negative for all of the four solvents. The negative Gibb’s energy suggests the spontaneous nature of dissolution process, whereas positive enthalpy indicates endothermic dissolution of compounds. The positive entropy is due to favorable dissolution in the studied solvents.

The solubility of isatin in different solvents was studied by a gravimetrical method from (298.15 to 318.15) K under atmospheric pressure and the solubility data were correlated against temperature. The solvents selected for the present study are: water, methanol, ethanol, 1-butanol, dichloromethane, dichloroethane, chloroform and carbon tetra chloride. Among chlorinated solvents, solubility is observed to be maximum in 1, 2-dichloroethane and minimum in dichloromethane whereas in alcohols, maximum solubility is observed in methanol. In water, solubility is found to be minimum. Further, some thermodynamic parameters such as Gibb's energy (ΔG sol ), heat of solution (ΔH sol ) and entropy of solution (ΔS sol ) have also been evaluated.

The solubility of enrofloxacin sodium in methanol, acetone, 1,2-dichloromethane, and 1,2-dichloroethane was measured by a gravimetrical method from (293.15 to 310.15) K under atmospheric pressure, and the solubility data were correlated against temperature.

The solubility of ofloxacin in 1,2-dichloromethane, chloroform, carbon tetrachloride, and water was measured by a gravimetrical method from (293.15 to 313.15) K under atmospheric pressure, and the solubility data were correlated against temperature. The solubility is at a minimum in water and a maximum in chloroform. Further, some thermodynamic parameters such as enthalpy, Gibbs energy, and entropy for dissolution have also been evaluated. For 1,2-dichloromethane and chloroform, enthalpy, Gibbs energy, and entropy values are very close and lower than those for carbon tetrachloride and water.

Some new dihydro pyrimidinone and pyrimidinethione compounds have been synthesized and their antibacterial activities have been studied in dimethyl formamide and dimethyl sulphoxide against some Gram positive and Gram negative bacteria. For this, Agar well diffusion method is used. It is observed that inhibition depends on solvent, bacterial strain, nature and position of substitution in a compound. When the same substitution is attached to different moieties its effect on bacterial strains changes in different solvents.