CEC of Ca-montmorillonite 0.93 meq/g; PZC=PZNPC; C and SSA flexible parameters!; C*SSA=91! (starting value SSA=100m^2/g; C=1F/m^2); SSA(BET)=21.4 m^2/g, SSA (EGME)=661.5 m^2/g); observation that pK1 very close to pK2 suggests that the acting group is >>Al(OH)OH2. SSD for »Al-OH: 0.000598mol/L, for »Si-OH: 0.000355mol/L