A small-scale semicontinuous pilot plant for studying chemical reactions carried out in remote environments is described. The all-stainless system features modular construction enabling rapid exchange of various elements. The equipment design permits purification, sampling, and other manipulative tasks to be performed in a“safe”operating area. Dissolved gases and moisture are removed from the reactant mass prior to circulation in the primary reaction loop. In this particular application, moisture is removed by low-temperature adsorption on molecular sieves. Progress of the drying is monitored continuously by a commercially available instrument in which moisture passes through a semi-permeable foil to a capacitance element. The rate of reaction in the remote reaction zone is reflected continuously in the time rate of change of conversion as measured by in situ differential refractometry. Utilization of this system has permitted accurate measurement of the rate of60Co radiation-induced polymerization under super-dry conditions.