42 Gas Analysis. V 
tracted from that found. A correction is then made for the 
volume of gas which remained in the diffusion tube and connec- 
tions after the sample was drawn. Corrections are also made 
for barometric pressure and temperature, for the volume of gas 
is always expressed as it would be at 0°C: and 760 mm. barometer. 
The following is an example of this calculation. 
Volume of air in diftusion tubes ere = 10.17) tees 
Volume taken for analysis. . gx = 9.440 “ (2) 
Nitrogen remaining after absorpuon Of oxygen. = 7.342“ (3) 
Oxygen absorbed, 7.e., (2)—(3).. ek = 25098 “7 4) 
Volume of atmospheric oxygen in Fone of 
20.93: 
gas taken for analysis, 7.e., (3) X re ae = (1.945 -Sa 
Oxygen from blood in volume of gas analyzed, 
€.6. (AYH(B) oe 5 seuss tee os oe cate ee 
1 
Total oxygen from blood, 7.e., (6) X ae oe = 0/168 * 
Oxygen reduced from barometric pressure 755 
and temperature 20° to 760 and 0°, 7.e., (7) X 
100 eo 5 ie ies oe en 0.147 “ (8) 
755. (278 + 20) 
Volumes per cent oxygen in blood, 7.e., (8) X 
L006 Te Ee eat, teat, = 14.7 
I 
* Tables for these factors of pressure and temperature will be found in 
any handbook of chemical constants. 
Comparative determinations of the oxygen content. of the blood 
by the Barcroft-Haldane method using the Brodie apparatus (5) 
and by our method gave the following results. 
Barcroft-Haldane method. _ Gas analysis method. 
16.2. 16.3 
16.5 16.1 
The two methods are we believe of approximately the same 
order of accuracy. To one accustomed to the use of the gas 
analyzer, but not in practice for the use of the Barcroft-Hal- 
dane method in its usual form, our modification is, we believe, 
decidedly the easier. 
The precision of the method may be increased,—at least 
theoretically—by filling the diffusion tube initially with nitrogen 
(from the analyzer) instead of air, inserting the stopper under 
