High-precision data for the coexistence curve of GeH//4 covering the reduced temperature range 10** minus **6 less than t less than 5 multiplied by 10** minus **2 have been derived from measurements of the refractive index by focal plane interference methods. The data are analyzed in terms of correction-to-scaling confluent singularities to yield the nonuniversal amplitudes. This is done by fitting the proposed theoretical expression to the data and by fixing the exponents to their renormalization group values. The data support the theoretical expression for absolute values of t approximately less than 10** minus **2.