?8 OPTICAL PROJECTION 



42. Purifying the Gas, Oxygen thus prepare! from 

 commercial chlorate is not fit to pass direct into the bag. 

 It is hot, and must be cooled ; it will contain a great deal of 

 free chlorine, and must be purified, else both bag and brass- 

 work will be rapidly destroyed. And it is very seldom 

 properly purified. Properly purified and dried, new jets and 

 taps should be used half-a-dozen times without any sign of 



FIG. 48. Arrangement of Purifier 



speak 



green corrosion being visible on the bright brass. I 

 from experience. 



The hot gas is passed through at least one cooler and 

 purifier, as shown in fig. 48, connecting the delivery-tube of 

 the retort by a piece of vulcanised tubing with the pipe which 

 goes nearly to the bottom of the purifier, and the tube which 

 leaves the top of the purifier, with the gas-bag or the next 

 purifier. Where only one purification is attempted, the whole 

 arrangement is shown in fig. 48, the gas bubbling up through 



