552 



ILL USTRA TI T E EXPERIMENTS 



For example: Normal blood — the first six tubes {i.e. 0-75 1 c.c.) are 

 clear, tube 7 shows scattering and slight haemolysis. Therefore (>1 c.c. 

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

 base equivalent to 0-84 grams NaHCO;^. This would, in Van Slyke's apparatus, 

 give rise to 224 c.c. of '" bound " COg — a somewhat high result (see p. 334), 

 due probably to interaction of acid and protein and to the buffering action 

 of the oxalate. 



In using this method for the determination of the alkali reserve of human 



blood, the endosmotic effect of the dilu- 

 tion of the blood by the acid ma;f* be 

 neglected as the salt concentration does 

 not fall to a value low enough to affect 

 the fragility of the corpuscles. It is ad- 

 visable, when sheep's or rabbit's blood is 

 used, to make up the acid in 0-75 per 

 cent, sodium chloride. It is also essential 

 to see that, if the blood is not used 

 immediately it is shed, that it is kept in an 

 ice chest and is brought to a tension of 

 COo equivalent to alveolar tension. (See 

 Van Slyke's method below.) 



(b) Alkali reserve. (C. J. Martin.) 

 Principle. Dilution of a well-buffered 

 solution such as plasma does not alter its 

 C^. 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 

 (100-1.50 c.c). 



Method. The flask is removetl 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 cent, (alcoholic) 

 neutral red. The optical effect of the turbidity of the plasma may be counter- 

 acted by placing a sheet of white tissue paper behind the tubes. The plasma 

 mixture is titrated with N'50HC'l (2 c.c. burette with fine nose) till its colour 

 matches the stantlards. Tliis is done by running the plasma into the flask, 

 adding a few drops of acid and rotating gently but steadily for 1 minute, the 

 flask meanwhile being in communication with the air. This readily allows 

 the thin film of plasma to give up the liberated COo. The fluid is run back 

 into the tube and compared with the standards. The process is repeated as 



VlH. 111. — Apparatus for cstiinalidii of 

 carbonates in solution. 



