Circulating pumps and flowmeters are two important units of circulating equipment used in investigations of the kinetics of reaction. The double-acting piston pump described is completely enclosed; its cylinder, its valves and the connecting tubing are made of glass, the piston of steel. The piston, suspended on a steel spring, is operated on an external magnetic coil fed by a square-wave generator. At resonance frequencies of 10-30 sec-1 the flow is constant (2000 cm3 min-1 at 1 torr delivery pressure, 1600 cm3 min-1 at 10 torr, 1200 cm3 min -1 at 20 torr). The flowmeter consists of a suitably counterweighted plate fitted to a horizontal bar, the whole being completely enclosed. In streaming gas, the plate deflects proportionally to the flow rate. The pressure drop caused by the meter remains below 1 torr. The whole of the device can be throughly flushed. The measuring range extends from 120 to 3000 cm3 min-1; accuracy is to ±10%. None of the components needs lubrication, nor are they liable to noticeable gas absorption.
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