A high-refractivity optical glass which has both a low-temperature softening property suitable for precision press-molding and glass stability suitable for hot-shaping of a preform, which contains, by mass %, 13 to 30% of B2O3, 0. The drive element is adjusted to a pre-definable minimum temperature and a pre-settable minimum temperature is maintained. The projected portion is moved depending on deformation of the flexible container, by urging of the flexible container, to stir the developer discharged from the opening. A strap is provided to lock the clamp closed. Additionally, the pumping device is powered by the recovered liquid expansion energy between the condenser and the evaporator.