A new versatile high pressure Heat Flux calorimeter has been developed and used to measure the heat of dissociation of methane hydrate. The calorimeter is completely automated, with an operating temperature range of $-50\sp\circ$C to 250$\sp\circ$C. It is a twin cell design with one liter sample volumes rated to 10,000 PSI. One sample cell is fitted with a magnetically driven stirrer and an internal electrical conductivity cell. The stirrer is used to assist in hydrate formation and the electrical conductivity cell is used to track hydrate formation.
The calorimeter has been calibrated both electrically and chemically and has been shown to have a sensitivity of 790 $\mu$Volts/Watt at 298 K. It can be operated in either isothermal or scanning temperature modes but has been used only in isothermal mode for the work reported here. Measurements were made of the heat of dissociation of methane hydrate at 5$\sp\circ$C, 43.00 atm and 10$\sp\circ$C, 72.54 atm. They were found to be, respectively, 13,770 and 12,716 calories per gmole of methane released. The associated pressures of 43.00, and 72.54 atm are those of the three-phase (liquid water, hydrate, methane gas) equilibrium conditions for the two temperatures.
Hydrate dissociation was accomplished by isothermally expanding the system volume. The rate of volume increase was controlled to match the gas expansion from the hydrate crystal in such a way as to maintain a relatively constant system pressure throughout the dissociation. This method not only simplified dissociation heat calculations, it also proved to be a very accurate means of identifying hydrate dissociation conditions.