594 METABOLISM 



shoulders (Fig. 180). It is then connected with the valves, the mouthpiece of which 

 is placed between the lips. Eespirations are commenced with the three-way valve 

 turned so as to allow the expirations to pass directly outside. After respiratory equi- 

 librium is established, the three-way valve is turned during an inspiratory period so 

 that the succeeding expirations may pass into the bag. The time required to fill the 

 bag comfortably is determined with a stop-watch. The air which has been collected 

 in the bag during the period is thoroughly mixed and passed through a meter, the 

 temperature and barometric pressure are noted, and a sample analyzed in the Haldane 

 gas-apparatus. The bag should be emptied completely by rolling it up when nearly 

 empty. 



5. THE HALDANE GAS-ANALYSIS APPARATUS. PRINCIPLE. The Haldane method of 

 analysis of expired air is simple and easily learned. The apparatus (Fig. 181) consists 

 of a gas burette, a control burette of the same size (both surrounded with a water 

 jacket), and bulbs containing dilute caustic potash or soda solution for the absorp- 

 tion of the carbon dioxide and an alkaline pyrogallate solution for the absorption of 

 the oxygen. The gas burette is connected with the bulbs by a two-way stopcock, which 

 allows a sample of gas to pass into either bulb. A control tube (10) is put into con- 

 nection with the burette through a manometer tube, which is connected with the alkali 

 bulb, and can be made to compensate for any changes in temperature that may occur 

 during the course of the analysis. For an analysis the gas is transferred to the burette 

 from the sampling tube, saturated with water vapor over mercury, and then measured, 

 after which it is transferred into the caustic solution to free it from CO 2 , and returned 

 to the burette to determine the loss of volume due to CO absorption. It is then trans- 

 ferred into the alkaline pyrogallate solution, which frees it from oxygen, after which 

 it is again brought back to the burette to determine the loss in volume due to the 

 absorption of the oxygen. 



THE APPARATUS. The detail of the Haldane apparatus is shown in the accompany- 

 ing cut. The measuring burette (1) holds 21 c.c. The bulb is of 15 c.c. capacity, 

 and the graduated stem, which is about 4 mm. in bore and 60 cm. in length, is grad- 

 uated to 0.01 c.c. from 15 c.c. to 21 c.c. The stopcock at the top of the burette is 

 double-bored, so that in one position air can be drawn in from a gas sampler (2) and 

 in another sent into the absorption bulbs (3). The lower part of the burette extends 

 through the rubber cork at the bottom of the water jacket (4). A piece of rubber 

 tubing is attached to the bottom of the burette and is passed through a metal tube 

 furnished on its inside with a metal disc which presses against the rubber tubing, the 

 pressure being controlled by means of a fine adjusting screw (). Below this a glass 

 stopcock (7) connects with rubber tubing to the mercury leveling bulb (5). The 

 absorption bulb for CO 2 , containing 20 per cent NaOH or KOH (5), is put in con- 

 nection with the burette by suitably turning stopcocks (3 and 8)* The control burette 

 (10) is also in connection with this bulb through the manometer tube (11).^ Any 

 variation in temperature which may occur during the analysis will cause the level of the 

 alkaline solution in the manometer to change. 



When final readings of the shrinkage of volume are made, the level of the caustic 

 solution is returned to the level of that in the manometer. By so doing any error due 

 to temperature changes is avoided, since change in temperature must be equal in the two 

 burettes. 



The absorption bulb for oxygen (12) is filled with a solution made by dissolving 

 10 grams of pyrogallic acid in 100 c.c, of a nearly saturated KOH solution. The 



*The stopcock (5) is double-bored, so that the tube leading from the burette can be brought into 

 connection with either 9 or 12. 



fThis tube also has a three-way stopcock (79), so that it may be opened to the outside. 



