198 Mr. Ivory oji the Constitution of the Atmosphere. 



p = k'g' i\+ud), I (1.) 



p = KR{l+ue): j 

 whence we deduce 



KR = kg=k'g';g = ~ R, g' = ^ R. 



The equations (1.) show that R, g, g' stand for the respective 

 densities of aii', oxygen, and azote, under the same pressure 

 p and the same temperature B: but it has been determined 

 experimentally that the three densities in such circumstances 

 are proportional to the numbers 1, 1'1057, 0"972: wherefore, 

 putting A = 1-1057, A' = 0*972*, we shall have 



e = A R, X ~ ^ 



g' = A> R, ^ = A'. 



Multiply the densities by the respective volumes, and take the 

 sum of the products; the result will be 



gu + g'v' = {Av -[^ A'o') R. 



Now gv+ g' v' is the sum of the masses of the oxygen and 

 azote ; and we may assume that this sum is equal to R V the 

 mass of the atmospheric air ; in consequence, by substituting 

 and leaving out the common factor R, we shall obtain 



Y = Au+ A'v'. 



This equation is not sufficient for determining v and v' when 

 a given value is assigned to V: we maj' therefore assume this 

 other condition, that i)-\-u' is equal to V, viz. 



V = o + u'. 



By means of the two equations, the values of u and u' will be 

 found, when V is given : thus V — 100, u = 20*9, u' = 79-0. 

 The conclusion is, that a volume of 21 parts of oxygen added 

 to a volume of 79 parts of azote, the pressure and tempera- 

 ture of both gases being the same, make 100 parts of atmo- 

 spheric air under the same pressure and temperature. 



The subject of mixed gases has been greatly perplexed by 

 conjectures about the question, whether particles of the dif- 

 ferent fluids in a mixture do, or do not, act mutually upon 

 one another. The difference of opinion on this point has 

 been carried so far, that some eminent chemists have had re- 

 course to a chemical combination of the gases, supposing that 

 air consists of atoms formed by the union of two atoms of 



* These numbers are taken from the Comptes Rendus , Sune 7. 1841. 



