Abstract Molar Cotton-Mouton constants and refractions are reported at 298 K for the following N-aralkylpyridinium cations as solutes in water or acetonitrile:(C 6 H 5) CH 2 (+ NC 5 H 5),(4-ClC 6 H 4) CH 2 (+ NC 5 H 5),(3-ClC 6 H 4) CH 2 (+ NC 5 H 5), 3-ClC 6 H 4) CH 2 (2′-Me+ NC 5 H 4),(4-NO 2 C 6 H 4) CH 2 (+ NC 5 H 5),(2, 5-Me 2 C 6 H 3) CH 2 (+ NC 5 H 5),(2, 5-Me 2 C 6 H 3) CH 2 (2′-Me+ NC 5 H 4),(2, 4, 6-Me 3 C 6 H 2) CH 2 (+ NC 5 H 5),( ...