Analysis of the Human Breath. 113 



A platinum spiral, heated to whiteness by a voltaic current, 

 was substituted for the carbonic oxide flame, — the object of this 

 being to compare the relative absorption, by air and breath, of 

 the heat emitted from the incandescent spiral and from the flame. 

 With the spiral as source, 30 inches of common air absorbed 5 

 per cent, of the total radiation, while an equal quantity of dried 

 air from the lungs gave almost exactly the same absorption. 



On April 26, experiments with the carbonic oxide flame were 

 renewed, for the purpose of making numerous measurements of 

 the absorption by air from the lungs taken at different periods, 

 and also to determine the amount of pure carbonic acid neces- 

 sary to produce the same absorption. The percentage of carbo- 

 nic acid in breath could then be calculated; and the amount 

 found by this means, compared with an accurate chemical analy- 

 sis, would show the reliability and advantages of this novel mode 

 of experiment. 



The experiments were conducted in precisely the same manner 

 as that already described. 



Two large vulcanized india-rubber bags, provided with suitable 

 stopcocks and connexions, were thoroughly cleansed, by dry air, 

 from any possible impurity. These bags were taken home, and 

 No. I. filled with air from the lungs about half an hour after 

 rising, and No. II. filled from the lungs of the same person 

 about 10 minutes after breakfast. A third and smaller bag was 

 also filled with air from the lungs after a brisk walk. 



Dr. Frankland very kindly undertook to analyze these differ- 

 ent specimens of breath, — the amount of carbonic acid in each 

 being determined by him with that precision which his own deli- 

 cate apparatus and high experimental skill enabled him to com- 

 mand. 



The same day on which the chemical analyses were made, the 

 absorption by the breath contained in each bag was ascertained, 

 and is given in the next Table. 



Table IV. — Carbonic oxide flame. 



Absorption 

 per 100. 



10-2 

 Bag No. I. . . {15 47-2 



Bag No. II, 



*c 



50-6 

 10-75 



52-8 



11-8 



Bas No. III. . <i 15 48-7 



53-7 

 Phil. Mag. S. 4. Vol. 28, No. 187. Aug, 1864. 



