An inversion of line profiles H and K Ca ii in the umbra of two sunspots is performed. By means of a numerical experiment, a tentative study of possible application of the method of intercomparison of lines in the multiplet (Goldberg's method) is made in cases when the condition of source function equality in multiplet is not fulfilled. It is found that the source functions of H and K lines in the sunspot umbra vary in a monotonous way. Their ratio in the layers for which measured values of ∆λD are available differs from unity. In the region of the lower chromosphere under consideration, the Doppler width is decreasing with height.