Solvent circuit

A circuit for the circulation of solvent to and from a valve having a rotatable first component having a circular cross section and an axis of rotation, the rotatable component provided with a first passageway, and a housing having a complementary circular cross section interior for rotatably housing the first component, the first component having a first orientation with respect to the housing in which the valve permits the flow of a valved fluid from a first port provided on the valve through the first passageway to a second port provided on the valve, the first component being rotatable to a second orientation with respect to the housing in which the valve prevents the flow of the valved fluid from the first port through the first passageway to the second port, a second passageway defined between the adjacent surfaces of the first component and the housing, a third port for the introduction of the solvent into the second passageway and a fourth port for removal of the solvent from the second passageway, the second passageway coupling the fourth port to the third port, the solvent being a solvent for the valved fluid, the solvent flowing substantially without interruption between the adjacent surfaces of the housing and first component without regard to the relative orientation of the first component and housing to flush residual valved fluid from the adjacent surfaces of the first component and the housing, a reservoir for the solvent, and means for coupling the third and fourth ports to the reservoir.