94 



Mr. W. Sutherland on the Law of Attraction 



experimental numbers we have to subtract from them the 

 cooling effects corresponding to the terms (PiV A — P 2 V A ). 



P V — P V 



Given that a volume V A of air is cooled by _i h 2 A ^ 



Js A 



and that a volume V B of C0 2 is cooled by 



PiV R -P 2 V, 



,we 



)• 



have for the cooling effect in the mixture : — 



1 / (Pi Va, ~ P 2 V A2 ) V A f A + (Pi Y Bl - P 2 V B ,) V B ,p B 



J ^ Y A 1 Pa S A + Y B 1 Pb S B 



In this manner the pv—p r v' part of the cooling effect of 

 the mixed gases has been calculated from the previously found 

 values for pure air and 00 2 . 



The table below contains in the first column the percentages 

 of the two gases in the particular mixture ; the second contains 

 the temperature (absolute) T at which the gas escaped ; the 

 third contains the total actual cooling effect for a difference of 

 pressure of 100 in. or 2*54 metres of mercury, observed by 

 Thomson and Joule (Phil. Trans. 1862) ; the fourth contains 

 the calculated values of the above expression for the cooling 

 effect to be subtracted; the fifth contains the cooling effect 6 

 obtained by subtracting the numbers in the fourth column 

 from those in the third ; while the sixth contains the values of 

 C obtained by substituting the corresponding values of 6 in 

 the equation for 6. 



Mixtures of Air and C0 2 . 



Percentage com- 

 position of 

 mixture. 



Absolute tem- 

 perature, 

 T. 



Total actual 

 cooling effect. 



Cooling effect 



to be 



subtracted. 



0. 



C. 



68 air \ 



280 

 280 

 280 

 323 

 323 

 364 



o 



176 



1-17 

 1-86 

 1-29 

 •88 

 1-1 



o 



•69 

 •45 

 •76 

 •49 

 •33 

 •36 



o 



107 



•72 

 1-1 

 •8 

 •55 

 •74 



•72 



•76 



•57 



•8 



•6 



•73 



32C0 2 j 



89 air 1 



11C0 2 J 



62 air \ 



38C0 2 J 



68 air 1 



32C0 2 J 



88 air \ 



12C0 2 J 



57 air 1 



43C0 2 j 



The agreement between these values of C calculated from 

 different mixtures at different temperatures is very fair, espe- 

 cially if the value *57 is left out of the count as being evidently 

 affected by some error in the experiment from which it is de- 

 duced ; because, if l o, 07 is correct for the first value of #, 



