402 RESPIRATION 



gr. 0.88) with distilled water to 1/2 50th, and the mixture shaken. The 

 ammonia solution prevents COg from coming off and also lakes the 

 blood. Unless the blood is laked, the ferricyanide cannot act on the 

 haemoglobin, since the corpuscle walls are impermeable to ferricyanide. 

 About 4 cc. of a saturated solution of potassium ferricyanide are then 

 poured into the small tube B (the length of which should slightly exceed 

 the size of the bottle) and placed upright in A. The rubber stopper, which 

 is provided, as shown, with a bent glass tube connected with the burette 

 by stout rubber tubing of about i mm. bore, is then firmly inserted, 

 and the bottle placed in the vessel of water C, the temperature of 

 which should be as nearly as possible that of the room and of the 

 liquid in the bottle. If the stopper is not heavy enough to sink the bottle, 

 the latter should be weighted. By opening to the outside the three-way 

 tap (or a T tube and clip) on the burette, and raising the leveling tube, 

 which is held by a spring clamp, the water in the burette is brought to 

 a level close to the top. The tap or T tube is then closed to the outside, 

 and the reading of the burette (which should be graduated to .05 cc, and 

 read to .01 cc.) taken after careful leveling, as soon as the temperature 

 has become constant, as shown by the constancy of the reading. Mean- 

 while the water gauge (which has a bore of about 2 mm.) attached to the 

 temperature and pressure-control tube is accurately adjusted to a defi- 

 nite mark. This is easily accomplished by sliding the rubber backwards 

 or forwards on the narrow glass tube D. The control tube is an ordinary 

 test tube containing some mercury to sink it. 



As soon as the reading of the burette is constant, the bottle is tilted so 

 as to upset B, and is shaken as long as the gas is evolved. During this 

 operation B should be repeatedly emptied, as otherwise the oxygen dis- 

 solved in its liquid might not be completely given off. When the evolution 

 of gas has ceased, the bottle is replaced in the water. If, as is probable, 

 the very sensitive pressure gauge indicates an alteration in the tempera- 

 ture of the water, cold water from a tap, or else warmed water, is added 

 till the original temperature has been reestablished, and the reading of 

 the burette noted as soon as it is constant. The bottle is again shaken, 

 etc., to make sure that the result is constant ; and usually about fifteen 

 minutes will be needed to complete the operations. The temperature of 

 the water in the jacket of the burette^ and the reading of the barometer 

 are now taken, and the oxygen evolved is reduced to its dry volume at 0° 

 and 760 mm. A table can be used for the reduction, and one is given in 

 Methods of Air Analysis. 



* The jacketing of the burette may be omitted, in which case the thermometer 

 should be suspended with its bulb close to the upper part of the burette. 



