Abstract. The viscosity of dry air at atmospheric pressure was measured by a capillary-tube method, at about 15°C. The ends of a wide-limbed U tube containing paraffin oil, of density 0.87, were connected by a pair of capillary tubes in series, so as to form a closed system. The oil was initially displaced, and in proceeding towards its equilibrium position it forced air through the capillaries. Care was taken to avoid constant and systematic errors, and two U tubes, two sets of capillaries and two methods of drying the air were used. Assuming that the viscosity increases by 4.93 × 10^-7 per °C., the value at 23°C. is (1834.7 ± 0.8) × 10^-7 c.g.s. units. The paper includes a summary of the general theory of the capillary-tube method and the correction terms involved, as well as a detailed theory of the present experiments.

Print publication: Issue 3 (1 May 1937)
Received 14 May 1936