With pulse techniques, determinations were made of double layer capacitance and numbers of hydrogen and oxygen atoms associated with a platinum surface undergoing anodic transitions to the oxygen evolution reaction. The complexity of hydrogen sorption on platinum was shown together with quantitative determinations of various hydrogen sorption regions. An improved definition of true surface area was possible because of the linearity of the atomic oxygen adsorption region and the precision with which the number of oxygen atoms on a fully covered surface could be determined quantitatively.