Indicator pK values for seawater

Clayton and Byrne (1993) determined pH as a function of Q for m-cresol purple at different temperatures and fitted this to an equation with the following result on the total hydrogen ion concentration scale (mol/(kg-seawater)), valid in the range 293 T 303 K and 30 5 37  

P/lhi for w-cresol purple is on the low side for optimum use in surface waters at low latitudes. Hence, Zhang and Byrne (1996) fitted Eq. (7-27) for thymol blue in the range 278 r 308 K and 30 5 40, on the total hydrogen ion concentration scale (mol/(kg-sea-water)), with Q being the ratio Asg(, A 2,5- 

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