We introduce a new parametric form for the phenomenological description of a static fluid (or ferromagnet) near a critical point. The new equations involving six parameters are easily remembered and manipulated. For a particular choice of one parameter (Ɗ), our equations reduce to the five parameter form suggested and applied by Ho and Litster. There appears to be a significant improvement in the fit to experimental data at small cost in complication if the sixth parameter is free. The present analysis is formulated in such a way as to facilitate the interpretation of interferometric measurements such as developed by Wilcox and Balzarini