In situ measurement of pH and dissolved H₂ in mid-ocean ridge hydrothermal fluids at elevated temperatures and pressures

This review covers the technological challenges in making accurate in situ measurements of pH and H₂ in hot hydrothermal vent fluids. Specific topics discussed include the theoretical considerations of sensor design, experimental verification, sensor design and construction, verification of sensor performance, sensor unit design for the seafloor deployment, in situ pH measurement, in situ dissolved H₂ measurements, long-term stability of YSZ ceramic in hydrothermal fluids and reference electrode for pH measurement.