Recent interest in bimesogenic liquid crystals showing two nematic phases has led us to investigate the nematic mean-field interactions in these nematic phases by using rigid solutes as probes. The nematic potential that is modelled by two independent Maier-Saupe terms is successful in fitting the observed dipolar couplings (molecular order parameters) of para-, meta-and ortho-dichlorobenzene solutes in both nematic phases of 39 wt.% 4-n-pentyl-4'-cyanobiphenyl (5CB) in alpha,omega-bis (4-4'-cyanobiphenyl) nonane (CBC9CB) to better than the 5% level. The derived liquid-crystal potential parameters G(1) and G(2) for each solute in the N and N-x phases are discussed. (C) 2012 Elsevier B.V. All rights reserved.