1891.] Formation of Carbonic Acid in Human Respiration. 63 



succession of pressures soon effected a perfect mixture. The mixture 

 was exploded as usual with a battery, when but little commotion was 

 produced. Then mercury was added through the open limb, and the 

 level adjusted in the two limbs ; a very short time sufficed to ensure 

 no further contraction or dilatation, and then the height of the 

 mercury was read off. In the calculation of the analyses a slight 

 correction was introduced, from the increased temperature of the 

 water in the jacket owing to the flash. 



This method proved extremely convenient and reliable. An 

 experiment could be commenced in the afternoon, say 4 o'clock ; the 

 combination with barium hydrate for the determination of C0 2 was 

 effected immediately after the air had been expired, and the turbid 

 fluid left till the following morning for titration. Next, air was drawn 

 into another cylinder by displacement with water, shaken with a solu- 

 tion of barium hydrate for about 12 minutes, and then the cylinder 

 was placed on the stand for the determination of the oxygen in the 

 air it contained. Fresh hydrogen was prepared for each experiment, 

 and, as stated before, it was, in nearly every case, tested with atmo- 

 spheric air before being used. 



The calculations of the analyses were made as follows : the volume 

 of the air expired, amounting to about 36 litres, was reduced to the dry 

 state, C., and 760 mm. pressure. This was done very rapidly by 

 means of the Table I have constructed for the purpose.* Then the 

 volume of C0 2 present was easily obtained from the weight of this 

 gas found in the analysis. Next, the volume of C0 2 was subtracted 

 from the volume of air expired, and the oxygen calculated on the re- 

 duced volume. With these data concerning the volume of air expired, 

 a Table was constructed, of which the following is an illustration : 



Table Illustrating the Results of an Experiment. 



Volume oxygen consumed 2106 c.c. 



Volume carbonic acid produced 1855 



Katio of oxygen consumed to CO 2 produced - 881 



Volume oxygen absorbed 251 c.c. 



Phil. Trans.,' 1890. 



