Refractive indices of binary and ternary mixtures formed by tetralin (1,2,3,4-tetrahydronaphthalene), isobutylbenzene (2-methyl-1-propyl benzene) and n-dodecane are presented over a wide range of compositions. All measurements of the refractive index have been conducted at 298.15 K and atmospheric pressure using two light sources: one in the visible (lambda = 670 nm) and the other in the infrared (lambda = 925 nm) spectrum. The concentration derivatives of the refractive index have been determined. The mixture compositions, where these two wavelengths are applicable for the measurements of mass transport coefficients by interferometry, are estimated and discussed. (c) 2013 Elsevier Ltd. All rights reserved.