Apparent molar volume and viscosity B-coefficients of N-alkylpyridinium halides in water

Apparent molar volume and viscosity data for some N-alkylpyridinium halides, viz. n-C3PyBr, n-C4PYCl, iso-C4PyBr, n-C4PyBr, nC(5)PyBr, n-C6PyBr and n-C8PyBr, in water (0.02 to 0.01 M) are reported at 25, 30, 35 and 40 C. The density data have been analyzed by Masson's equation and the molar volumes (m) and slopes (S-v(*)) are interpreted in terms of ion-solvent and ionion interactions, respectively. The viscosity results obey the Jones-Dole equation; the constants A and B suggest an increase in ion-solvent interaction with increase in alkyl chain length. The magnitudes of parameters dB/dT and dB(ion)/dT, which are positive and negative, respectively, for all salts except N-butylpyridinium chloride indicate that while the undissociated salts are structure breakers, the N-alkylpyridinium ions are strong hydrophobic structure-making ions. Branching in the alkyl chain does not appear to have much influence on the solute-solvent interactions of these salts.