Apparatus (10) for automatically dispensing a liquid treatment chemical (12) from a replaceable supply bottle (14) into an intermittently flowing liquid stream (22) such as a recirculating water supply for a refrigeration system. The apparatus has a feeder chamber (16) into which the liquid stream (22) flows which is periodically emptied by a siphon tube (18) when the liquid reaches a level sufficient to establish a siphon effect in the siphon tube (18). The rising level of liquid (22) in the chamber (16) also actuates, by means of a float (24), the valve portion (31) of a closure assembly (30) on the inverted top of the supply bottle (14). The valve portion (31) is fed by a capillary tube (50) and dispenses a predetermined, very small quantity of chemical each time it is actuated. The valve portion (31) is prevented from becoming clogged by chemical crystals during inactive periods by being mounted so that its surface will be flushed each cycle by the water (22) which rises in the feeder chamber (16).