Conductivities of some tetraalkylammonium halides, viz. tetrapentylammonium chloride (Pen(4)NCl), tetrahexylammonium chloride (Hex(4)NCl), tetraheptylammonium chloride (HeP4NCl), and tetraoctylammonium chloride (Oct(4)NCl) were measured at 298.15 K in THF + CCl4 mixtures with 40, 60 and 80 mass% of THF. A minimum in the conductometric curves (molar conductance, A vs. square root of concentration, c) was observed at concentrations which is dependent both on the salt and the solvent. The observed molar conductivities were explained by the formation of ion-pairs (M+ + X- <-> MX, K-p) and triple-ions (2M(+) + X- <-> M2X+; M+ + 2X(-) <-> MX2-, K-T). A linear relationship between the triple-ion formation constants [log(K-T/K-p)] and the salt concentrations at the minimum conductivity (logC(min)) was given for all salts in THF+CCl4 mixtures. The formation of triple-ions might be attributed to the ion sizes in solutions in which coulombic interactions and covalent bonding forces act as the main forces between the ions (R4N+ ... X-). (c) 2008 Elsevier B.V. All rights reserved.