COMPOSITION AND PROPERTIES OF ATMOSPHERIC AIR. 229 



continuously the air in the chamber. This air is first conducted into the vessel b 

 which is tilled W1 th pumice-stone saturated with water. Here the air becomes 

 saturated with aqueous vapor, and then passes through the gasometer c, which 

 indicates the total volume of the interchanged air; tht latter is then discharged 

 into the outer atmosphere. 



The main tube x, leading from the chamber, carries a mercurial manometer q 

 9 r the detection of possible variations in pressure within the room This tube 

 gives off a branch tube n, through which the air passes for chemical examination 

 I he air in this tube is driven by a suction-apparatus M M 1? constructed on the 

 principle of Muller s mercurial valve, and worked by the same steam-engineias 



.FiG. 88. Diagram of v. Pettenkofer's Respiration Apparatus. 



the pump P Pj. Before entering the pump the air passes through the sulphuric- 

 acid bulbs, from whose increase in weight the amount of aqueous vapor can be 

 estimated. After leaving the pump the air passes through the tube R, filled with 

 baryta-water, which absorbs the carbon dioxid. The quantity of air passing 

 through the branch tube n is then measured by the gasometer u, after which it 

 finally passes into the atmosphere. The second branch tube N provides for^an 

 examination of the air before entering the chamber, by an apparatus identical 

 with that placed on the tube n. The excess of carbon dioxid and water found 

 in n over that in N is due to the respiratory activity of the subject placed in the 

 chamber. 



COMPOSITION AND PROPERTIES OF ATMOSPHERIC AIR. 



The dry atmosphere contains: 



Percentage in Percentage in 



Gas. Weight. Volume. 



23.015 20.922 Including i per cent, in 



N 76.985 79- 02 volume of argon, together 



CO 2 0.029-0.034 with helion, and i part of 



krypton in 20,000 parts of 

 air. 



The air contains likewise xenon, neon, coronium (lighter than hydrogen), 

 and less than one-millionth part of aetherium (which latter possesses a specific 



