Experimental techniques were discussed to control or measure the chemical potential of components and the transport phenomena in solid state cells. Ion blocking techniques for the Hebb-Wagner d.c. polarization study were discussed using the (-) Ag/AgX (X = Cl, Br, I)/C or Pt (+) cells. It was shown that complete ion-blocking is realized when the chemical equilibrium is attained not only at the Ag/AgX but also at the AgX/C (or Pt) interface. Several types of cells and measuring techniques were demonstrated to determine the electronic conductivity, chemical diffusion coefficient and nonstoichiometry in AgX. For the kinetic studies of the electrode reaction at the porous gas electrode in solid oxide fuel cells (SOFC), techniques for the determination of the length of the triple phase boundary of the gas/porous electrode/electrolyte were discussed. For the oxide cathodes, methods to evaluate the contribution of oxygen diffusion in the oxides were sought for by the measurement of oxygen released from the oxide electrode.