ALKALI RESERVE OF BLOOD 417 



to the water till it has approximately the same pH as the bicarbonate. 

 Titrate both with N/50HC1 to the same end point. 



(ii) To demonstrate the effect of the tension of C0 2 on the pH of a solution 

 of bicarbonate. Put 5 c.c. of a 0-25 per cent, solution of NaHC0 3 in each 

 of three tall stoppered cylinders. To each add 2 drops of neutral red. 

 Fill (a) with air expired after a deep inspiration, (b) with alveolar air (Expt. 

 43) and (c) with C0 2 from a generator or cylinder. Stopper and shake. 

 Note colours. Remove the C0 2 in (c) by repeated changes of atmospheric 

 air. Note that the colour goes back from crimson through the red of (6) 

 to the orange of (a) or even to the yellow seen before any C0 2 was added. 



41. An Approximate Determination of the Alkali Reserve of Blood. 

 (Rieger.) Principle. Erythrocytes are easily damaged by acid. This 

 will lead to agglutination and haemolysis on the addition of acid as soon 

 as the reserve of base has been used up. 



Method. Twelve test tubes (8" x 1" or thereabout) cleansed thoroughly 

 and dried are set in a rack. The first or stock tube is charged with 18 c.c. 

 of a 0-85 per cent, solution of NaCl (pure salt in distilled water) and 2 c.c. 

 of whole blood (oxalated with 0-2 per cent, pure sodium oxalate). Mix 

 thoroughly by drawing up into the pipette several times, keeping the tip 

 of the pipette always below the surface of the liquid. 



One c.c. of the diluted blood is placed in the bottom of each tube, avoiding 

 the sides, and then, starting on the left, N/100HC1 is added from a graduated 

 pipette. The first is given 0-7 c.c. acid, the next 0-75 and so on, increasing 

 the amount by 0-05 c.c. with each tube, the last tube thus receiving 1-20 c.c. 

 In about an hour examine the tubes. Those on the left should show no 

 haemolysis and the corpuscles should be settled in a sharply defined clump 

 in the centre of the foot of the tube. The tube on the right may show 

 haemolysis and have corpuscles scattered over the bottom in an irregular 

 manner, giving a speckled appearance. The tube with the greatest amount 

 of acid which shows no haemolysis or scattering of corpuscles gives an 

 indication of the alkali reserve of the blood. 



For example : Normal blood the first seven tubes (i.e. 0-7-1 c.c.) are 

 clear, tube 8 shows scattering and slight haemolysis. Therefore 0-1 c.c. 

 of blood can neutralise 1 c.c. of N/100 acid, or 100 c.c. of blood contains 

 base equivalent to 042 grams NaHC0 3 . This would, in Van Slyke's 

 apparatus, give rise to 112 c.c. of " bound " C0 2 a somewhat high result 

 (see 42 and 43), probably due to interaction of acid and protein. 



42. Alkali Reserve. (C. J. Martin.) Principle. Dilution of a well- 

 buffered solution such as plasma does not alter its C H . If an indicator 

 is used which has a low protein error the plasma may be titrated with acid. 

 The titration value indicates the acid-combining power of the plasma. 



Apparatus. A small wooden stand to hold three " non-sol " glass test 

 tubes (8 x 0-8 cm.) vertically in a row and close together. The central tube 

 at its upper end runs through the rubber stopper of an inverted " non-sol ' 

 flask (100-150 c.c,). 



Method. The flask is removed from the central tube and 0-5 c.c. of 

 plasma or serum and 2 c.c. of neutral 0-9 per cent, sodium chloride added. 

 The side tubes are almost filled with a phosphate buffer mixture of pH = 7-4. 

 These standard tubes are coloured by the addition of a drop of two aqueous 

 solutions of burnt sugar and flavine (1/100,000) till they match the fluid 

 in the central tube. To all of the tubes are then added 2 drops of 0-05 per 

 B.B. 27 



