Applications involving the semiconductor‐electrolyte interface require a good understanding of charge carrier transport at the interface and the related concept of Fermi level in an electrolyte. The meaning of electrolyte Fermi level is currently an active research question. As an experimental approach to the problem, we have developed a convenient technique, using a Kelvin probe. Using this, we can measure the surface potential without making contact to the solution. An important question is how the surface potential is related to the solution composition. We find that surface potential depends on thepH of the solution in a well‐defined way. From our data, we can estimate the absolute emf of the hydrogen electrode. The result agrees well with published values, determined by other means.