layer   pH  ionic strength
  1 5.94718 7.03715
  2 5.95707 7.04080
  3 5.96701 7.04466
  4 5.97698 7.04875
  5 5.98700 7.05308
  6 5.99700 7.05768
  7 6.00716 7.06258
  8 6.01731 7.06781
  9 6.02751 7.07342
 10 6.03775 7.07942
 11 6.04804 7.08587
 12 6.05838 7.09281
 13 6.06878 7.10030
 14 6.07923 7.10837
 15 6.08978 7.11653
 16 6.10051 7.12375
 17 6.11130 7.13168
 18 6.12291 7.14007
 19 6.13381 7.14948
 20 6.14478 7.15978
 21 6.15583 7.17104
 22 6.16696 7.18334
 23 6.17816 7.19676
 24 6.18946 7.21136
 25 6.20084 7.22723
 26 6.21232 7.24446
 27 6.22390 7.26314
 28 6.23559 7.28333
 29 6.24739 7.30512
 30 6.25931 7.32861
 31 6.27135 7.35387
 32 6.28353 7.38095
 33 6.29584 7.40995
 34 6.30829 7.44092
 35 6.32090 7.47393
 36 6.33366 7.50905
 37 6.34659 7.54630
 38 6.35970 7.58578
 39 6.37299 7.62746
 40 6.38647 7.67142
 41 6.40015 7.71777
 42 6.41404 7.76643
 43 6.42814 7.81756
 44 6.44247 7.87119
 45 6.45704 7.92745
 46 6.47186 7.98642
 47 6.48693 8.04834
 48 6.50227 8.11346
 49 6.51788 8.18214
 50 6.53379 8.25484
 51 6.55000 8.33230
 52 6.56653 8.41529
 53 6.58339 8.50513
 54 6.60061 8.60330
 55 6.63080 10.1297
 56 6.64878 10.1503
 57 6.66689 10.1710
 58 6.68513 10.1920
 59 6.70350 10.2131
 60 6.72199 10.2343
 61 6.74061 10.2557
 62 6.75936 10.2771
 63 6.77823 10.2984
 64 6.79723 10.3198
 65 6.81634 10.3408
 66 6.83558 10.3612
 67 6.85494 10.3807
 68 6.87441 10.3985
 69 6.89398 10.4133
 70 6.91363 10.4232
 71 6.93333 10.4222
 72 6.95294 10.4372
 73 6.97210 10.5000
 74 7.00000 10.6500
 75 7.02223 10.8000
 76 7.03879 10.9929
 77 7.05868 10.9545