278 Mr. Ivory o}i the Constitution of the Atmosphere. 



great energy, and the evolution of deutoxide of azote. It is 

 converted into a resin, and on adding a salt of baryta an 

 abundant precipitate of sulphate of baryta is obtained. Sul- 

 phuric acid first reddens, and with the assistance of heat, chars 

 it. It dissolves iodine readily, but without explosion 

 Glasgow, Hth October, 1841. 



I 



XLI. On the Constitution of the Atmosphere. By James 

 Ivory, K.H., M.A., Hon. M.R.I.A., Instit. Reg. Sc. Paris, 

 et Reg. Soc. Gotting. Corresp.* 



N the last Number of this Journal (p. 197) I assumed that 

 the atmosphere is composed solely of oxygen and azote : 

 but besides these gases, it is found to contain a small propor- 

 tion of carbonic acid gas, the quantity of which has been in some 

 decree appreciated. It may not therefore be improper briefly 

 to resume the subject, in order to take in all the constituent 

 parts of the atmosphere, as far as they are known, leaving 

 out the consideration of aqueous vapour, which requires a 

 separate discussion. Suppose three several portions of oxy- 

 gen, azote, and carbonic acid gas, their common temperature 

 beinf^, and their pressures, densities, and volumes being re- 

 presented respectively by p, p, v, p\ p', v', p", p", v" ; and let 

 the three gases be confined in an envelop, the volume of 

 which is V = v + v' + v". According to the theory of mixed 

 gases, as explained in this Journal for February last (p. 81), 

 each of the three gases will be uniformly diffused through the 

 envelop, and the elasticity of the mixture, resulting from the 

 mutual action of the three elasticities, will be 



and if we suppose p = p' = p", the same elasticity will be 

 simply j>. Let R be the density of atmospheric air, the press- 

 ure being p and the temperature 6 : then the four densities 

 R, p, p',p", will be proportional to the numbers 1, 1*1057, 

 0-972, 1*52 tj for which we may write 1, A, A', A": so that 

 we shall have 



p = A . R, 



p' = A' . R, 



p"=A". R: 

 and if we multiply the densities by the respective volumes, 

 and add the products, there will result 



vp + v'p' + v<'p" = {Av + A'v' + A" v") R. 



* Communicated by tlie Author. 



t The more exact number is 1-5196.— Biot, Precis de Phyt. 



