Introduction:In-situ measurement of pH under high pressure has been a challenge.It is hypothesized that the lethal effects of pressure can be attributed in part to decreases in pH arising from electrostriction.However,the lack of suitable devices for pH measurement under pressure has resulted in the need to use reaction volume data to calculate and infer pH under high pressures.Most such methods rely on the assumption that the chemical equilibria which exist at atmospheric pressure may be extrapolated to apply under high pressures.