Table 2. Summary of the Optimization of Pitzer Parameters for the CaSO₄–H₂SO₄–H₂O System^a.

		Ca2+–SO42– ion interaction									Ca2+–HSO4– ion interaction
		β(0)			β(1)			β(2)			β(0)			β(1)			Cϕ
model	OF	a	bT	f/T	a	bT	f/T	a	bT	f/T	a	bT	f/T	a	bT	f/T	a	bT	f/T
set-0b	0.23				D		D	D	D		x	x	x	x	x	x	x	x	x
set-1b	0.23				D		D	D	D		x	x	x	x	x	x	x	x
set-2b	0.71				D		D	D	D		x	x	x	x	x	x
set-3b	0.30				D		D	D	D		x	x		x	x	x	x	x
set-4b	0.39				D		D	D	D		x	x	x	x	x		x	x
set-5b	0.22	x	x		D		D	D	D		x	x	x	x	x	x	x	x
set-6	0.16				x		x	x	x		x	x	x	x	x	x	x	x

^aThe parameters of Gibbs energy changes for forming the solid phase use the A + B × T + C × T ln T form.

^bValues of parameters β⁽¹⁾ and β⁽²⁾ for Ca²⁺–SO₄^2– ion interactions are from model D in a previous work⁷ and kept unchanged in the assessment.