(In most cases, but not necessarily all, H would be equal to the local work-function; certainly this is true for metals.) The issue is how to determine the value of B by experiment. There are two obvious ways. (1) Suppose that eq. (43) can be used to determine a reasonably accurate experimental value of κ, from the slope of a plot of form [−dln{ i }/d(1/ V) vs. V ]. In this case, a second plot, of ln(i)/ V vs. 1/ V, should be an exact straight line of slope − B. This approach should be the most accurate way of determining B.