McKubre, M.C.H., et al. Calorimetry and Electrochemistry in the D/Pd System. in The First Annual Conference on Cold Fusion. 1990. University of Utah Research Park, Salt Lake City, Utah: National Cold Fusion Institute. CALORIMETRY AND ELECTROCHEMISTRY IN THE D/Pd SYSTEM Michael C.H. McKubre, Romeu C. Rocha-Filho*, Stuart Smedley, Francis Tanzella SRI International Jason Chao, Bindi Chexal, Tom Passell, and Joseph Santucci Electric Power Research Institute * On leave from the Federal University of Sao Carlos, Brazil ABSTRACT Experiments have been performed to examine the anomalous effects associated with the D/Pd system, and to discover some of the experimental variables that might be important to the effects. Experiments were concerned with calorimetry of the D/Pd system, but also monitored those experimental variables that might be important in causing the effects: the D/Pd ratio and its rate of change, interfacial phenomena such as the reduction of D 2 O, or reduction of contaminant species. Two types of calorimeters were employed: a differential calorimeter and a flow calorimeter. In both of these instruments the electrochemical cell was pressurized with D 2 gas to 60 atm. The calorimeters were designed to facilitate on-line measurement of the resistance of the Pd cathode, and for high quality measurements of the interfacial impedance. In both calorimeters the electrochemical system has produced evidence of heat output appearing in bursts, apparently in excess of known input power sources. These bursts last for several hours or tens of hours, and produce energies up to several hundred thousand joules. In electrodes that are heavily loaded with D, the electrical resistance of the Pd cathodes was observed to pass through a maximum with increasing time of cathodic charging, which is consistent with the known behavior of the H/Pd system. The electrochemical interfacial impedance of the cathode gives evidence of one, and at times two relaxation phenomena; it is also sensitive to accumulation of cathodically deposited impurities that may influence the rate and degree of D loading. INTRODUCTION Following the announcement last year by Fleischmann, Pons and Hawkins [1] of anomalous effects in the D/Pd system, we have performed a series of experiments designed to examine anomalous excess enthalpy associated with this system and to discover some of the experimental variables that might be important to the effects. We have designed our experiments with two important principles in mind: the need in precise calorimetric measurements for a closed system, and for knowledge at all times of the composition of the reacting system. These principles were based on the understanding that calorimetry in an open system is subject to more error than in a closed one; this is especially