Two test loops have been designed and utilized at REPUBLIC GEOTHERMAL, INC'S. (RGI's) East Mesa test site to study the properties of geothermal fluids. These test loops are suited for determining critical fluid properties such as phase separation, liquid and gas composition as a function of thermodynamic conditions, scaling tendency, etc. They also have been used to study the effects of chemical alteration of the fluid with acid or scale inhibitor addition in order to avoid scale formation. The loops are easy to construct and handle. Their operation does not interfere with other test work being performed to evaluate additional well and reservoir properties. They are well suited for gathering information about the fluid properties at the very earliest stages of field development. Such early data is essential in order to avoid mistakes in field development and power plant design which might result if critical fluid properties are neglected