THE IiNDIVIDUAL GROUPS OF PROTEINS 499 



(i) Haldanes Method. 



Haldane 1 originally estimated the oxygen and oxygen capacity 

 in an apparatus which was almost identical with the Dupre apparatus 

 for estimating urea and the estimation can be performed in such an 

 apparatus. The graduations of the burette should be to 0*05 c.c. 



20 c.c. of (defibrinated) blood are measured out with a pipette 

 and introduced into the blottle of about 120 c.c. capacity. The last 

 drops of blood must not be blown out, but are expelled by closing 

 the top of the pipette with the finger and warming the bulb with the 

 hand. 30 c.c. of dilute ammonia solution (i part ammonia of sp. gr. 

 880 in 500 parts distilled water) are added and mixed with the 

 blood. The ammonia prevents the evolution of carbonic acid whilst the 

 water lakes the corpuscles. The solution should be quite transparent. 

 If the laking be not complete, more ammonia must be added. 4 c.c. 

 of saturated potassium ferricyanide solution are put in the small tube, 

 which should be slightly longer than the width of the bottle, and it is 

 placed upright in the large bottle without spilling. The bottle is 

 closed with a rubber stopper through which a glass T-tube passes ; 

 this is connected at one end with a burette in a cylinder of water by 

 india-rubber tubing and closed at the other end with a clip. The 

 bottle is put in a vessel of water of the same temperature as that of 

 the room. By opening the clip, the level of the water in the burette 

 is brought nearly to the top and to the same height as the water in 

 the cylinder. The clip is closed and the height in the burette is- read 

 off. The bottle is tilted so as to upset the ferricyanide solution and 

 shaken gently as long as gas is evolved, the little tube being repeatedly 

 emptied so that all the oxygen is given off. When the oxygen 

 ceases to be evolved, the bottle is replaced in the water and cold or hot 

 water is added to it until it attains the same temperature as at the 

 commencement. (This is shown by means of a pressure gauge for very 

 accurate work, as in Haldane's apparatus, Fig. 66.) The burette is 

 adjusted so that the water has the same level inside and outside and 

 the volume of the gas is read off. The difference in readings gives 

 the amount of oxygen evolved from 20 c.c. of blood. 



This volume should be reduced to o and 760 mm. and a correction 

 should be made for the pipette which delivers only about 19*6 c.c. 

 of blood instead of 20 c.c. of blood. Further, in very accurate work 

 account must be taken of the air in the bottle, which has become 

 richer in oxygen ; oxygen is twice as soluble as nitrogen. 



!J. Physiol., Vol. 2 



