SCIOPTICON MANUAL. 173 



A conical sheet-iron retort, b, about a foot high, with 

 joints "up set" and hammered close, is cheaper than 

 the copper retort in common use; is handier, stands 

 firmer, lasts longer, and can be new-bottomed by any tin- 

 smith when burnt out. When new, the seams should 

 be luted with moistened clay or plaster of Paris, and 

 whenever used the cap c must be luted on. 



Fig. 46. 



The cap has the same bevel as the retort, tapering 

 into a bent tube, the end of which is covered by the 

 flexible tubing d. The gas when liberated by heat passes 

 through this tubing, first down the long pipe into the 

 water, near the bottom of the wash bottle e, then bub- 

 bling up, washed and cooled, it passes over and into the 

 gas bag 0. It will be noticed that connections are made 

 in all our apparatus, by slipping the flexible tubing over 

 the ends of the brass pipes, which either have tapering 

 nipples, or are cut with a slant on the under side. 



THE OPERATION OF COLLECTING OXYGEN GAS. Pour 

 the charge into the retort, seeing that no chips or other 

 materials enter with it. Let the wash bottle be less 



