The neutron diffraction patterns of liquid rubidium have been measured for momentum transfers between 0.4-2.4 Å-1 for twelve states between 328-473 K and 10-1200 atmospheres using the IN4 spectrometer at the Institut Laue-Langevin. These states were chosen to give isothermal, isochoric and isobaric data. In this paper we present the experimental results and the isothermal pressure derivatives of the liquid structure factor. The latter may be predicted from a model in which the electron fluid is assumed to control the position of the ions, so that when it is compressed all inter-ion distances vary as (density)-1/3. The experimental derivatives are close to the predictions of the model, and some interpretations of this observation are given