pH scale: SWS (according to Yao and Millero, 1995, p. 82: "refitted if necessary")
Total (according to Lewis and Wallace, 1998)
We stick to SWS here for the time being
The fits from Millero (1995) and Yao and Millero (1995)
derive from Millero et al. (1988), with all the coefficients
multiplied by -ln(10)