Date of manufacture:
Designed to deliver warmed ether vapour of an adjustable and known concentration.
'The temperature of the ether remains constant because it is jacketed with crystals of hydrated calcium chloride which are, in their turn, surrounded by hot water in the chamber. This vaporiser probably affords the most accurate method known of giving an air-ether mixture and has been used successfully under service conditions during the late war. It is particularly useful in maintaining a very light plane of narcosis'
(Hewer, Recent Advances in Anaesthesia, Ed 6, 1948.)
Before use, the Calcium Chloride Hexahydrate crystals are melted by running very hot water through the water chamber, then the water is drained. This process of preheating takes approximately 20 minutes and several changes of very hot water. The heat of crystalisation of calcium chloride provides a constant temperature of 30°C for vaporisation until crystallisation is complete. The device includes an unidirectional inlet valve, a spring-loaded, self-inflating bellows and a second unidirectional valve close to the mask. This arrangement permits artificial, controlled or assisted ventilation by manually compressing the bellows.
N.B. The tetrahydrate, CaCl2.4H20 crystals melt at 45.5°C.
Macintosh R. R., Lancet II, 61, 1941.
B/W illustrations are from Minnitt & Gillies, 'Textbook of Anaesthetics', 7th Edition, (1948) Livingstone,Edinburgh.