120 0// a Physical Analysis of the Human Breath. 



having analyzed only the first four, the other determinations 

 remained unchecked. 







Table XIV. 







Absorption 



f *" 

 By 30 inches 

 of breath. 



per 100 



By pure car- 

 bonic acid 

 and dry air. 



Tension of CO 2 , 



in parts of an 



inch. 



Percentage of carbonic 

 acid found 



Bag 



No. 



t i 



By absorp- By chemical 



tion. analysis. 



I. 



. 50-6 



50 ; 7 



1-2 



4-00 4-311 



II. 



. 52-8 



526 



1-4 



4-66 4-556 



III. 



. 53-7 



53-7 



1-55 



5-16 4061 



IV. 



. 54-0 



54-0 



1-6 



5-33 5*212 



V. 



. 50-0 



50-0 



1-15 



3-83 



VI. 



. 52-7 



52-6 



1*4 



4-66 



VII. 



. 50-0 



50-0 



1-15 



3-83 



VIII. 



. 52-1 



520 



1-3 



4-33 



The percentage of carbonic acid found in bags No. II. and IV. 

 only vary 0*1 from the chemical analysis \ even this small dif- 

 ference will disappear in extended and repeated experiments. 

 In bag No. I. the difference amounts to 0*3 per cent. : this 

 would be considerable in a chemical analysis; but bearing in 

 mind the small data upon which the physical determinations are 

 made, it is sufficiently near to prove the correctness of the prin- 

 ciple and the general accuracy of the observations. Bag No. III. 

 shows a difference of upwards of 1 per cent, between the physical 

 and chemical analyses. This anomaly has already been referred 

 to, and may be accounted for by supposing that the material 

 of w T hich the bag is composed had imparted to the breath con- 

 tained in it an impurity which could not be detected by chemical 

 analysis, but which strongly influenced the more delicate mode 

 of experiment. 



In order to make these preliminary experiments complete, and 

 to imitate as nearly as possible the condition of the breath as it 

 entered the experimental tube, the following experiment was 

 made. 



A glass bolt-head, having rather a larger capacity than the 

 brass tube, was fitted with a cap and stopcock and well exhausted. 

 It was connected with the gauge of the air-pump, and also with 

 drying-tubes, leading to a gas-holder containing carbonic acid. 

 A stopcock was now carefully opened, and 1*4 inch of dry car- 

 bonic acid allowed to enter the bolt-head. The stopcock was 

 then promptly closed, the drying-tubes and gas-holder removed, 

 and pure dry air caused to fill the glass vessel. Thus a mixture 

 was obtained containing 1*4 part of carbonic acid, and 28*6 

 parts of pure air, this being about the average composition of 



