Oxygen Buffers in Field and Laboratory

The buffer assemblage in the outer capsule fixes /hj this controls HCl activity in the inner capsule according to the equilibrium 

Probably the simplest use of fo minerM buffers is to include the buffer assemblage as part of the total system being studied. For example, the assemblage pyrite + pyrrhotite + magnetite fixes /oj at any T and P by the reaction 

At the same time, this three-phase assemblage fixes /sj. 

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