APPENDIX 



423 



pressure is never likely to become great enough to cause 

 danger. 



When the generator is used outside the lantern, the artificial 

 evaporation produced by the passage of oxygen cools the vessel, 

 and the formation of the ether-gas is thereby retarded. This is a 

 serious drawback, especially as the gradual emptying of the ether 

 chamber leads to the same result, i.e. the lessening of the ether 

 supply. 



A saturator to combine the advantages of both these forms was 

 designed in the laboratory of Christ's College, New Zealand, and is 

 made by Messrs. Newton & Co. (fig. 238). It consists of a brass 

 cylinder A, closed by a screw cap B. At c is a stopper for filling. 

 The space above c is filled with two rolls of 

 concentric packing material separated by a 

 brass tube. On the top are two nozzles, a. 

 double one E D and a single one F. 



The oxygen supply is connected to D, and 

 divides into two branches, passing upwards out of 

 nozzle E to the oxygen tap of an ordinary mixed 

 gas-jet, the other path leading downwards into 

 the saturator, through the outer roll of packing 

 material, into the chamber below c, upwards 

 again through the inner roll of packing and 

 emerging at F, charged with ether vapour, and 

 on to the ordinary hydrogen tap of the jet. 



Below c is a hollow space filled with liquid 

 ether, and from the packing chambers are hung 

 long cotton wicks into this tank of ether. These 

 wicks draw up the liquid by capillary action to 

 take the place of that absorbed by the oxygen, 

 and thereby the porous material in the upper 

 chamber is kept fully saturated. 



The advantages of this form of generator are 

 threefold : 



(1) The construction renders it easy to with- 

 draw the rolls of packing material for drying 



purposes, and this should be done at least once every season, as 

 ether contains an appreciable quantity of moisture which does not 

 evaporate readily, and therefore accumulates. 



(2) The saturator being kept full by means of the cotton wicks 



Fio. 238 



