5(50 METABOLISM 



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 con- 

 trol tube (10) is put into connection with the burette through a manometer 

 tube, which is connected with the alkali bulb, and can be made to com- 

 pensate 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 C0 2 , and returned to the burette to determine the loss of 

 volume due to C0 2 absorption. It is then transferred 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 accompanying 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 graduated 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 (o). The lower part of the burette ex- 

 tends 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 (6). Below this a glass stopcock (7) con- 

 nects with rubber tubing to the mercury leveling bulb (5). The absorption 

 bulb for C0 2 , containing 20 per cent NaOH or KOH (#), is put in con- 

 nection with the burette by suitably turning stopcocks (3 and <).* 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 pyogallic acid in 100 c.c. of a nearly saturated 

 KOH solution. The specific gravity of the KOH should be 1.55, which is 

 obtained approximately by dissolving the sticks (pure by alcohol) in an 



*The stopcock (8) is double-bored, so that the tube leading 1 from the burette can be brought into 

 connection with either 9 or 12. 



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



