ACIDOSIS 45 



livered into A (which has been rinsed out with C0 2 -free ammonia water), 

 and the stopcock / turned so that by cautiously lowering the level of the 

 reservoir F, the plasma runs into B (but no trace of air). The same 

 procedure is repeated with 1 c.c. water, so as to wash in all of the plasma, 

 and finally 0.5 c.c of 5 per cent H 2 S0 4 is sucked in, after which stopcock I 

 is turned off. The reservoir F is then lowered sufficiently to allow all 

 of the mercury, but none of the blood, to run out of B and C. A vacuum 

 is thus produced in B and C. 



As the level of the mercury falls in B and C, the plasma effervesces vio- 

 lently,* because it is exposed to a vacuum. To be certain that all traces of 

 C0 2 have been dislodged from the solution, the apparatus is inverted 

 several times. To ascertain how much C0 2 has been liberated, stopcock // 

 is now turned so as to bring C and E into communication, and by cautiously 

 lowering the reservoir the fluid in C is allowed to run into the bulb E. 

 Stopcock // is thereafter turned so as to connect C and D, and the reser- 

 voir raised so that the mercury runs into C as far as the C0 2 that has col- 

 lected in the burette will permit it to go. After bringing the level of the 

 mercury in F to correspond to that in the burette, the graduation at which 

 this stands is read. It gives the c.c. of C0 2 liberated from the plasma. 

 Under the above conditions normal plasma binds about 75 per cent of 

 its volume of C0 2 ; therefore, since the total capacity of the pipette is 50 

 c.c., the mercury should stand at 0.375 c.c. on the burette. For accurate 

 measurement it is necessary to allow for the C0 2 that remains dissolved 

 in the water, etc., as well as for barometric pressure and temperature. 

 This is best done by the use of a table based on the known solubility of 

 C0 2 under the various conditions obtaining, which is given in Van 

 Slyke's paper. 12 



The Haldane-Bar croft apparatus that is most suitable for the above 

 analysis is shown in Fig. 136, page 382. t One c.c. of C0 2 -free ammonia 

 water is placed in the bottle and the 1 c.c. of plasma delivered beneath it. 



*This may be prevented by adding a small drop of caprylic alcohol. 



tThis form of Haldane-Barcroft apparatus is not quite the same as the differential manometer 

 that is used for measurement of the (^-combining power of hemoglobin (page 382). In the form 

 used for the present purpose, a side tube at the bend of the U-tube is connected with a small rub- 

 ber bag, which can be compressed by a screw. When the gas is evolved in the bottle, it presses 

 down the fluid in the proximal limb of the manometer correspondingly and raises that in the distal 

 limb. Since the calculation of the amount of gas evolved depends on finding the pressure produced 

 without any change in volume, it is necessary after the gas has been evolved to compress the rubber 

 bag until the meniscus of fluid in the proximal limb of the manometer is brought back to its original 

 level. The height at which the fluid stands in the distal limb then obviously corresponds to the 

 pressure created by the evolved gas. 



The equation for determining the amount of gas evolved depends on the gas law, which states 

 that the pressure of a gas is inversely proportional to its volume (page 336). Suppose that the 

 volume of gas evolved was equal to the volume of the bottle, then, since the volume has been 

 kept constant, the pressure would be doubled that is, the fluid in the distal limb would equal that 

 of 1 atmosphere, or 10,400 mm. of water or 10,000 of clove oil, which is the fluid actually used to 

 fill the manometer. Any other observed pressure would therefore correspond to the volume of 

 evolved gas according to the equation, 



vol. of bottle (and tubing to meniscus) 



V = i A nnn e u \ ^~~- T; X mm. Pressure in manometer. 



10,000 (when clove oil is used) 



In using the apparatus in the above manner, only one of the bottles is employed, and the tartaric 

 acid is added from a pocket in the stopper by a simple manipulation. 



