Abstract: A solvent proportioning arrangement for liquid chromatograph apparatus comprises a plurality of solvent sources connected to a proportioning valve arrangement. A control arrangement controls the proportioning valve arrangement so that each solvent is connected for an appropriate time interval to the inlet of the pump during its return (or suction) stroke. When the time interval required to proportion a given percentage of one solvent is such that it is less than a reliable operating time for the proportioning valve the control arrangement causes the valve to cause n times the required proportion to be presented every nth cycle.