In this work the Newtonian gravitational constant G was determined with high precision. The constant of gravitation is a measure of the strength of the gravitational attraction. In this experiment, the gravitational force of two large movable stainless steel vessels, filled with in total 13.5 tons of mercury, changed the weight difference measured on two 1.1 kg masses. The amplitude of this change was determined with a commercially available beam balance. The starting point of the present work was a determination of G with a relative uncertainty of 220 ppm in 1998. A large part of this uncertainty was caused by a possible nonlinearity of the beam balance. In this work, the influence of this nonlinearity was considerably decreased by means of a new averaging method, for which a special calibration handler was developed. The relative uncertainty of the described measurement is 32.8 ppm. The value is in agreement with most of the values previously obtained with other methods.