A full range of solid solutions (N-2)(x)Ar-1-x (0 < x < 1) have been e
xamined with an x-band microwave dielectrometer. The real part of the
permittivity epsilon' versus temperature T for this non-polar system h
as been measured with a high accuracy (10(-6)) at temperatures between
1.5-75 K. A comparative (x, T) phase diagram is constructed with a be
ta-alpha structural phase transition and the problem of transition to
the orientational glass is discussed.