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.