### Abstract

Regular solution theory indicates that solubility parameters of crystalline organic compounds can be estimated from solubilities in London solvents. The equation for this purpose is: IN X_{2} - ΔH_{f} RT_{f} (T_{f}-T) T + ΔC_{p} R (T_{f} - T) T - ln T_{f} T - V_{2}θ^{2}_{1} RT (δ_{1} - δ_{2})^{2} where X_{2} is the mole fraction solubility of a compound in a solvent with a solubility parameter of δ_{1}. With the exception of ΔC_{p}, all parameters in the equation necessary to estimate the solute parameter, δ_{2}, can either be suitably approximated or readily determined experimentally. In order to use the equation, simplifying assumptions have been made concerning ΔC_{p}, namely: ΔC_{p} = 0 or ΔC_{p} = ΔS_{f}, the entropy of fusion. In the present work, we have considered the extent to which these assumptions influence the magnitude of solubility parameters estimated from solubilities in n-hexane, n-heptane, n-dodecane, cyclohexane, carbon tetrachloride, toluene and benzene. Using n-alkyl p-aminobenzoates as test compounds, it is shown that solubility-based solubility parameters are relatively insensitive to the form of the equation used to calculate δ_{2}. Specifically, solubility parameter estimations based on the two simplifying assumptions differ by no more than 0.2 (cal/ml)^{ 1 2}, an increment of the order of the presumed inherent error of estimation.

Original language | English (US) |
---|---|

Pages (from-to) | 223-229 |

Number of pages | 7 |

Journal | International Journal of Pharmaceutics |

Volume | 49 |

Issue number | 3 |

DOIs | |

State | Published - Feb 1 1989 |

### Fingerprint

### ASJC Scopus subject areas

- Pharmaceutical Science

### Cite this

*International Journal of Pharmaceutics*,

*49*(3), 223-229. https://doi.org/10.1016/0378-5173(89)90346-3