DATABASE T&H.DAT   # from www.xs4all.nl/~appt
PRINT; -reset false; -user_pr true
SURFACE 1
# For Psi vs I (= ionic strength) dependence, adapt specific surface A in PHRC:
# A = 159300 - 220800/(I)^0.09 + 91260/(I)^0.18
# Example: A = 34170 m2/g for I = 0.01 mol/L
# 1 g humic acid
  H_a  7.10e-4  42.93e3  1
  H_b  7.10e-4; H_c  7.10e-4; H_d  7.10e-4

  H_e  3.55e-4; H_f  3.55e-4; H_g  3.55e-4; H_h  3.55e-4

  H_ab 1.18e-4; H_ad 1.18e-4; H_af 1.18e-4; H_ah 1.18e-4
  H_bc 1.18e-4; H_be 1.18e-4; H_bg 1.18e-4; H_cd 1.18e-4
  H_cf 1.18e-4; H_ch 1.18e-4; H_de 1.18e-4; H_dg 1.18e-4
  -equil 1
  -diffuse_layer                         # diffuse layer calculations included
SOLUTION 1
  pH  7.0
  Ca  1
  Na  1;  Cl  2 charge
USER_PRINT
 -start
 10 HCa = mol("H_aCa+") + mol("H_bCa+") + mol("H_cCa+") + mol("H_dCa+")\
        + mol("H_eCa+") + mol("H_fCa+") + mol("H_gCa+") + mol("H_hCa+")
 12 HCa = HCa + mol("H_abCa+") + mol("H_adCa+") + mol("H_afCa+") + mol("H_ahCa+")\
        + mol("H_bcCa+") + mol("H_beCa+") + mol("H_bgCa+") + mol("H_cdCa+")\
        + mol("H_cfCa+") + mol("H_chCa+") + mol("H_deCa+") + mol("H_dgCa+")
 20 dl_Ca = edl("Ca")*2 - edl("water") * tot("Ca") * 2
 22 if dl_Ca < 1e-20 then goto 200
 30 dl_Na = edl("Na") - edl("water") * tot("Na")
 32 dl_Cl = edl("Cl") - edl("water") * tot("Cl")
 40 cec = abs( edl("Charge"))
 50 I = (tot("Na") + tot("Ca")*4 + tot("Cl"))/2
 52 print 'Ionic strength :', I
 60 print 'charge on HA   :', cec, 'eq.',  '        excess Na+Ca-Cl in dl = ', dl_Na + dl_Ca - dl_Cl
 62 print 'K_Ca\Na for dl =', mol("Na+") / mol("Ca+2")^0.5\
              * (dl_Ca / cec)^0.5 / (dl_Na / cec)
 64 print
 66 print 'dl_Na     = ', dl_Na, 'dl_Ca     = ', dl_Ca, 'complexed Ca =', HCa
# find Donnan conc's...
 70 v_D = 1e-3 * 0.24 * I^-0.42
 80 a = tot("Ca") / (tot("Na"))^2
 90 D_Na = (-1 + (1 + 8 * a * cec)^0.5) / (4 * a)
 92 D_Ca = a * D_Na^2
100 print 'Donnan_Na = ', D_Na,  'Donnan_Ca = ', D_Ca,  'counter ions =', D_na + 2*D_Ca
200 end
 -end
END
SURFACE 2
# 1 g humic acid
  H_a  7.10e-4  27.72e3  1
  H_b  7.10e-4; H_c  7.10e-4; H_d  7.10e-4

  H_e  3.55e-4; H_f  3.55e-4; H_g  3.55e-4; H_h  3.55e-4

  H_ab 1.18e-4; H_ad 1.18e-4; H_af 1.18e-4; H_ah 1.18e-4
  H_bc 1.18e-4; H_be 1.18e-4; H_bg 1.18e-4; H_cd 1.18e-4
  H_cf 1.18e-4; H_ch 1.18e-4; H_de 1.18e-4; H_dg 1.18e-4
  -equil 2
  -diffuse_layer                         # diffuse layer calculations included
SOLUTION 2
  pH  7.0
  Ca  1
  Na  100;  Cl  2 charge
END