ZUNTZ-GEPPERT APPARATUS. 57 



Zuntz has devised an automatic method for indicating a volume of 

 100 c.c. of air at the conditions under which the air passes through the 

 meter. A thin-walled metal capsule containing a few drops of water is 

 placed inside the air-tube G entering the meter and another in the 

 tube T leading from the meter. The location of these capsules is 

 shown at C and D in figure 20. The two capsules are connected by a 

 small metal tube s, s, which in turn is connected with the graduated 

 glass tube, P, shown at the side of the meter. This graduated tube is 

 partly filled with water and actuated by a leveling tube, Z. The 

 method of use is as follows: The volume, 100 c.c. at 0° C. and 760 mm. 

 pressure, is calculated to the volume at the average temperature of 

 the meter and the barometric pressure, the latter being corrected for 

 the tension of the aqueous vapor in the meter at the time of use. A 

 stopcock, K, at the side of the graduated glass tube, P, is opened to the 

 air and air is drawn into the graduated glass tube by means of the 

 leveling tube, Z, to the point corresponding to the volume calculated. 

 The glass stopcock, K, is then closed. The reading of the graduated tube 

 gives the volume of 100 c.c. at the observed temperature and pressure. 



Automatic sampling device. — Another arrangement connected with 

 the meter provides for taking automatically a small sample from the air 

 as it enters. To the central axis of the meter, which is extended at the 

 back, are fastened 4 or 5 concentric pulleys of different sizes (see U). 

 Around one of these pulleys passes an endless cord, r, r, r, which is 

 carried over pulleys at the top of the meter and then forward to pulleys 

 on the front of the meter. These are shown in figure 20 at E, E, and F. 

 This endless cord then extends downward to a loose pulley, M, some- 

 what below the level of the meter. The cord is kept taut by the weight 

 L. Upon the right-hand side of the cord as it is carried over the two 

 pulleys E and E, is attached a glass overflow tube, N, with an open end, 

 which is connected by a rubber tube to the bottom of the analytical 

 apparatus at J. The weight of the overflow tube, N, and of the rubber 

 connections is counterpoised by means of the weight X. Theoretically 

 the weight of the exit tube and connections should be greater than the 

 weight used to counterbalance it, so that no pressure will be produced in 

 the meter and thus hinder respiration. 



The routine of sampling is as follows: Before an experiment is begun, 

 the measuring burettes, 1 and 1 , on the gas-analysis apparatus are filled 

 with acidulated water. The overflow tube N is then lifted to a height 

 somewhat above the zero-mark on the burettes. As all of the connec- 

 tions are open, each movement of the meter lowers automatically the 

 tube N so that the water-levels in the sampling burettes, 1 and 1 , are 

 at the same time gradually and automatically lowered. The rapidity 

 with which this is done can be regulated by placing the cord on different 

 pulleys at the back of the meter. The air is thus drawn through the 

 sampling tube, Q, Q, which extends from the large ingoing air-pipe G 



