Precision flow-microcalorimeter.

Abstract

A design for a flow-microcalorimeter is described. The instrument uses a two hundred junction thermopile detector between twin calorimeter regions. Mixing of two thermally equilibrated solutions is accomplished without a vapor space or mechanical stirring in one of the twin cells. The attendant heat effects are measured using servo-controlled electrical heating. Well controlled thermal shields are used to provide both precise thermal equilibration of the solutions and adequate isolation for the twin calorimeter elements. Heat effects of 1 mcal have been measured with a precision of 1% for a steady state experiment where two reactants are mixed together at equal flow rates of 10−3 cc/sec and the attendant heat effects are measured during a 100 sec time interval. A pulsed flow experiment in which mixing of 0.1 cc of each reactant is allowed to occur for the same time interval is also feasible, but gives measurements with lower precision.