Figure 3: Frequency graph for the
test case with only activity correction at low and high ionic strengths.
Phosphoric acid test
case
This test case is a simple chemical test, which is interesting in this
context because of the PO43- species.
We find that all the algorithms reach 100 % resolution (Table 5) in
fewer than 70 iterations. The frequency graph shows that the full Newton
algorithm usually converges within the fewest iterations and that the
inner fixed-point algorithm requires the most iterations to converge.
Nevertheless, the outer fixed-point algorithm provides very interesting
results for this test case: it converges within 36 and 39 iterations
regardless of the initial guess.