ADVANCED DEMONSTEATIONS 405 



The volume of gas given off equals the volume of air in the blood-gas 

 tube and connections multiplied by the corrected reading of the gauge 

 in millimetres and divided by 10,300. 



For example, supposing the reading of the gauge = 100; the total 

 capacity of the blood-gas vessel and connections to the zero of the 

 gauge = 23-35 c.c. ; and the capacity minus the volume of liquid within 

 it = 23-35 -2-75 c.c. = 20-6 c.c. ; then the volume of oxygen given off 



100 



= 20-6 x = -20 c.c. If the temperature were 14, then the 



lUjOUU 



volume of gas at standard pressure (760) and temperature (0) would 



273 

 be -20 x -^~ = -19 c.c. = 19 c.c. per 100 vols. blood. 



The vapour tension of the ammonia used gives an error of about 3 mm. This 

 can be determined by a blank experiment omitting the ferricyanide. The 

 capacity of the blood vessel is ascertained by weighing it empty and full of water. 

 The capacity of the connecting tubing is determined by adjusting the gauge to 

 zero, and then raising the pressure to a certain definite amount, first with the 

 vessel connected, and afterwards with a stopper inserted into the end of the 

 rubber tube in place of the glass tube of the vessel. The capacity of the vessel 

 and connecting tube will be to that of the connecting tube as the first reduction 

 in volume in the right-hand limb of the gauge is to the second. 



The stopper of the blood-gas vessel is now removed, and *25 c.c. of 

 20 per cent, tartaric acid solution placed in the pocket, the stopper 

 replaced and the gauge adjusted to zero in the same way as before. 

 The acid is then spilt, and the bottle shaken till all the C0 2 is set free. 

 The gauge is again read off and the volume of C0 2 calculated as in the 

 case of oxygen. 



As the co-efficient of absorption of the blood mixture for C0 2 is 

 found to be 1 at the temperature of observation, the volume of gas must 

 in this case be calculated from the capacity of the blood-gas vessel 

 without subtracting the volume of the contained liquid. 



A slight correction is necessary for the C0 2 in the liquids used. This 

 may be determined by doing a blank experiment, mixing boiled distilled 

 water with the ferricyanide and ammonia solution. 



Example of results obtained by this method : 



DEFIBRINATED BLOOD. THREE SAMPLES. 

 2 . C0 2 . 



18-5 52-4 



18-5 52-7 



18-8 61-2 



