Seifert Fibre Groups (SF-Gps) have been introduced and their first derived groups have been worked out in an earlier paper by the author [2,3]. Now we aim to prove that they are residually soluble and residually finite.

The Extended Hildebrand solubility Parameter Approach (EHSA) is used to estimate the solubility of satranidazole in binary solvent systems. The solubility of satranidazole in various water-PEG 400 mixtures was analyzed in terms of solutesolvent interactions using a modified version of Hildebrand-Scatchard treatment for regular solutions. The solubility equation employs term interaction energy (W) to replace the geometric mean (d1d2), where d1 and d2 are the cohesive energy densities for the solvent and solute, respectively. The new equation provides an accurate prediction of solubility once the interaction energy ‘W’ is obtained. In this case, the energy term is regressed against a polynomial in d1 of the binary mixture. A quartic expression of ‘W’ in terms of solvent solubility parameter was found for predicting the solubility of satranidazole in water-PEG 400 mixtures. The expression yields an error in mole fraction solubility of ~2.17%, a value approximating that of the experimentally determined solubility. The method has potential usefulness in preformulation and formulation studies during which solubility prediction is important for drug design.

The modified square well potential is combined with perturbed-hard-trimer-chain (PHTC) EOS to predict the solubility parameters of several fluids including alkanes, refrigerants and molten polymers. The performance of the proposed model has been evaluated by predicting the solubility parameters of 12 hydrocarbons, 3 refrigerants and 12 polymers. Out of 263 data points for hydrocarbons and refrigerants, the average absolute deviations percent (AAD%) of the predicted densities and solubility parameter from the experimental ones were found to be 1. 74% and 1. 09%, respectively. Additionally, out of 1993 data points of 12 polymers, the AADs% of the predicted densities were found to be 0. 43% and out of 60 data points examined, the AAD% of the predicted solubility parameters from the experimental ones were found to be 0. 56%, respectively.