QUANTITY AND COMPOSITION OF BLOOD 



859 



solution are thoroughly mixed by shaking, and at the end of this operation the solution 

 should appear perfectly transparent when tilted up against the sides of the bottle.* 

 About 4 c.c. of a saturated solution of potassium ferricyanide are then poured into the 

 small tube B (the length of which should slightly exceed the width 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 1 mm. bore, is 

 then firmly put in, 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 blood and water 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 T-tube and clip) on the 

 burette, and raising the levelling tube, which is held by a spring clamp, the water in 



FIG. 370. Haldane's method for determining the oxygen capacity of the blocd. 



the burette is brought to a level close to the top. The tap is then closed to the outside, 

 and the reading of the burette (which is graduated to -05 c.c., and may be read to -Olc.c.) 

 taken after careful levelling. 



The water-gauge (which has a bore of about 1 mm.) attached to the temperature 

 and pressure-control tube is now accurately adjusted to a definite mark. This is easily 

 accomplished by sliding the rubber tube backwards or forwards on the piece of glass 

 tubing D. The control tube is an ordinary test-tube containing some mercury to sink 

 it, and connected with the gauge by stout rubber tubing of about 1mm. bore. 



As soon as the reading of the burette is constant, which it will probably be within 

 two or three minutes, the bottle is tilted so as to upset p., and is shaken as long as gas is 

 evolved . During this operation B should be repeatedly emptied, as otherwi se the oxygen 

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

 oxygen has ceased the bottle is replaced in the water. If, as is probable, the pressure- 

 gauge indicates an alteration in the temperature of the water, cold water from the tap, 

 or warmed water, is added till the original temperature has been re-established, and the 



* If the solution were not transparent this would indicate that the laking was 

 incomplete, and more ammonia solution would need to be added. 



