EPR spectra using perdeuterated 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxy as spin probe on a mixture of p-n-octyl-p'-cyanobiphenyl and p-n-decyl-p'-cyanobiphenyl at a 0.30106 mole fraction for p-n-decyl-p' -cyanobiphenyl revealed the existence of a tilt angle that has been attributed to the longer p-n-decyl-p'-cyanobiphenyl molecules. Temperature control to within +/-0.01 degreesC revealed the existence of two-phase regions across the smectic A-to-nematic and the nematic-to-isotropic transitions which point to first-order transitions.