ZUNTZ-GEPPERT APPARATUS. 59 



b and b are closed, thus furnishing connection between the overflow tube 

 N and the burettes. Next to the two sample-measuring burettes, 

 1 and 1, are two more burettes, 2 and 2, which are graduated from 90 

 to 100 c.c. and are used for measuring the gas after the carbon dioxide 

 has been absorbed. These are connected by the Y connections, c 

 and c, and d and d, to the caustic-potash pipettes, H and H, and to the 

 phosphorus pipettes, I and 7, respectively. On the inside of these 

 burettes are two additional burettes, 3 and 3, graduated from 75 to 86 

 c.c, in which the gas is measured after the oxygen has been absorbed 

 in the phosphorus pipettes, I and I. Y connections at the top (e and 

 e, and/ and/) lead to the phosphorus pipettes, I and I, and to the open 

 air, respectively. The connections between the pipettes and burettes 

 are made by means of capillary rubber tubing, and closure is made of 

 this rubber tubing by means of spring clamps, as shown in figure 20. 

 In the center of the seven burettes is the special burette, 4> known as 

 the " analysis thermo-barometer." Corrections for changes in baro- 

 metric pressure and the temperature of the water-bath are made by 

 means of the readings taken upon this burette. The burette 4 at the 

 beginning of the experiment is filled with a definite amount of water; 

 the stopcock is then closed at the top and the reading taken by means of 

 the leveling bulb F, which is at the right of the figure. When a read- 

 ing is made, the water-levels in the arms of the leveling bulb and that 

 in the burette are brought to the same horizontal plane. 



Routine of gas analysis. — The analysis of the air is carried out as 

 follows: After the sample has been drawn into burettes, 1 and 1, the 

 pinchcock on the tube JN is closed, and the pinchcocks k, k and h, h 

 are opened; after a few minutes a reading is taken, using the leveling 

 bulb, F, at the right. A simultaneous reading is taken of burette 4 — 

 the so-called "analysis thermo-barometer." Several readings are taken 

 at intervals of a minute or so until the changes in all three burettes 

 are alike or give constant readings. The air in these two burettes is then 

 driven over into the pipettes H and H by opening the pinchcocks b and 

 b. When all of the gas has been driven into the pipettes, the pinchcocks 

 are closed, and the gas is allowed to remain for at least 10 minutes to 

 insure complete absorption of the carbon dioxide. The leveling bulb 

 F is then lowered and hung on a hook at the right-hand side of the 

 tank, the pinchcocks c and c being opened so that the gas will descend 

 slowly into burettes 2 and 2. The gas should be drawn into these 

 burettes very slowly in order that they may drain properly. After 

 the gas has been drawn in, the solutions in the two caustic-potash 

 pipettes H and H are drawn to the same point that they were before 

 the analysis was started. The pinchcocks c and c are then closed and 

 readings are taken of burettes 2 and 2, and of the analysis thermo- 

 barometer, 4, until they become constant. The gas is then driven into 

 pipettes I and I, which contain stick yellow phosphorus. Here the 



