LABORATORY WORK 201 



the level of the mercury is the same in both. Read the volume of 

 the gas. 



Add I or 2 c.c. of strong sodium hydroxide through the cup 

 after lowering the reservoir. The volume of the gas will diminish, 

 owing to absorption of carbon dioxide. Next add in the same way 

 I or 2 c.c. of pyrogallol. Nearly the whole of the rest of the gas 

 will be absorbed showing that it is oxygen. The small residue is 

 nitrogen. 



We now want to see whether the blood which has lost oxygen 

 can take it up again and give it off to a vacuum. We must first 

 wash out the pump by running in water and expelling it from the 

 side by the stopcock D, until it comes away colourless, finally 

 rinsing out with 0.9 per cent, sodium chloride. 



Now rotate the bottle containing the dark blood so that a thin 

 film is formed over the interior. The blood becomes bright red 

 again. Repeat the process of removing the gas by the pump, noting 

 how much blood is used. We obtain practically the same volume 

 of oxygen as before, taking account of the respective quantities of 

 blood used. 



To be satisfied that it is the corpuscles and not the plasma that 

 has this function, the experiment may be repeated with serum or 

 plasma. A little oxygen may be given off if haemolysis has occurred 

 and the serum is red. Colourless serum can be obtained by allow- 

 ing blood to clot and to stand until the serum has exuded from the 

 clot and can be collected in a pipette. 



Absorption Spectrum. After exposure to oxygen there are two 

 bands in the yellow of the spectrum, best seen in very dilute 

 solution of haemoglobin in water. Addition of a drop of blood 

 from the finger to a test-tube full of water will serve. Add more 

 water if too concentrated. The addition of a few drops of a 

 reducing agent, such as ammonium sulphide, and warming, changes 

 this spectrum to one of a single band. Shaking with air brings 

 back the original two bands for a sho# time. 



It may be thought more convincing to remove the oxygen by 

 the pump. Take a dilute oxy-haemoglobin such as shows the two- 

 banded spectrum in a tube of the same diameter as that of the 

 pump. Fill the pump with mercury, and then run in gently 2 or 

 3 c.c. of the solution. Observe with the spectroscope whether the 

 two bands can be seen. If so, close the stopcock and lower the 

 mercury vessel. Drive out the gas given off through the cup C. 

 It will not be entirely reabsorbed during the operation. Repeat until 

 the spectroscope shows the single band. A small relative amount of 

 the oxy-haemoglobin is sufficient to show the double band. 



Carnage of Carbon Dioxide. To show that haemoglobin also 

 carries carbon dioxide, it is necessary to remove the serum from the 



