THE RESPIRATION APPARATUS. 



49 



of air through the U 

 tubes and meter at a 

 proper rate of flow, while 

 the water is ordinarily 

 turned on and off by the 

 valve w,,. At t a glass T 

 tube is inserted for the 

 rejection of air (see p. 

 77), to the stem of which 

 a rubber tube dipping 

 into a small vial contain- 

 ing water is attached. 

 The rubber tube is ordi- 

 narily closed with a screw 

 pinchcock, the tightness 

 of the closure being 

 proved by the absence of 

 bubbling of water in the 

 small vial. 



The water used for act- 

 uating the suction-pump 

 enters at m and passes 

 into the large chamber F, 

 which serves as a trap. 

 This chamber consists of 

 2-inch gas-pipe with a cap 

 at each end. To prevent 

 sediment from clogging 

 the fine jet of the water- 

 pump, the supply of 

 water for the pump itself 

 is drawn from a point 

 somewhat above the bot- v 

 torn of the trap. The 

 sediment in the water col- 

 lects below this point, and 

 can be drawn off through 

 the valve ze> 2 , which is 

 always opened a moment 

 or two before starting 

 the suction - pump. To 

 prevent the entrance of 

 air in the water current, a 

 43 



FIG. 19. Apparatus for Drawing Sample of Air for Residual 

 Analysis. A glass suction-pump A draws air from the 

 Elster meter and delivers it, together with the water used 

 for aspiration, into separating chamber B. The water 

 flows off through overflow through pipe d and the air 

 passes through exit tube t into drying chamber D. 



