Apparatus is described in which a clean sodium surface is continuously presented for reaction with hydrogen by means of a jet. A miniature electromagnetic pump is used to circulate the molten metal. Rates of reaction of hydrogen with sodium over the pressure range 10 to 15 cmHg have been measured at temperatures between 224 and 303 °C. The reaction obeys first-order kinetics and an activation energy of 17·3 kcal mol–1 was calculated for the process. A comparison is made with results obtained by other techniques.