The electrical ignition of mixtures of ether vapour, air, and oxygen

Explosions of ether-air or ether-oxygen mixtures have occurred from time to time in operating theatres, some of them with fatal results. Those having an electrical origin might oftenhave been prevented had the conditions of electrical ignition of such mixtures been known. The proportions of ether and oxygen and air within which ignition is possible vary with the type ofsource. With hot wires, such as cauteries, ignition can occur within limits as wide as 3 to 80 per cent of ether in oxygen. With sparks, in general the limits are much narrower. The work described determines these limits and the least currents that cause ignition when broken slowly or suddenly, or by fusing wires. Second only to hot wires as a possible risk are the fizzling sparks at a slower intermittent break of circuit between fine wires. When the current is kept below certain well-defined values it is found that ignition can always be prevented. It is then only necessary to specify that the. total resistance of the circuit for any given voltage shall besuch that these currents cannot under any circumstances flow in the circuit. A factor of safetyof 2 is ample for this purpose.