TABLE 225. 



COEFFICIENTS OF THERMAL EXPANSION. 



Coefficients of Expansion of Gases. 

 The numbers obtained by direct experiment on the change of volume at constant pressure, E P , are separated in the 



column of i atm. have been made for all pressures near to 76 centimetres of mercury. The other numbers in the 

 pressure columns are centimetres of mercury at o C. and approx. 45 latitude, unless otherwise marked. 



constant pressure. 



pressure coumns are centmetres o mercury at o . an approx. 45 lattude, unless otherwise marked. 

 Thomson has given (vide Kncyc. Brit. art. "Heat") the following equations for the calculation of the expan- 

 sion, , between o and 100 C. of the gases named. Expansion is to be understood as change of volume under 



= .3662(1 .00049 J/r ) 

 v 7'o ' 



= .3662(1 + .0026 } 

 v o ' 



E = .3662 (i -f .0032 ) 

 i> ' 



= .3662(1 +.0031 *>) 

 o' 



E .3662 (1 + .0164 \ 

 v a > 



where V /v a is the ratio of the actual density of the gas at o C. to the density it would have at o C. and one 

 atmosphere of pressure. The same experiments (Thomson & Joule, Trans. Roy. Soc. 1860), which, together 

 with Regnault's data, led to these equations, give for the absolute temperature of melting ice 2.731 times the 

 temperature interval between the melting-point of ice and the boiling-point of water under normal atmospheric 

 pressure. 



Hydrogen . 

 Common air . 

 Oxygen . . . 

 Nitrogen 

 Carbon dioxide 



* Corrected by Mendelejeff to 45 latitude and absolute expansion of mercury. Rowland gets almost the same 

 correction on Regnault, using Wiillner's value of the expansion of mercury. 



t The series of results at different pressures are given because, of their interest. The absolute values are a little 

 too low. (See preceding footnote.) 



SMITHSONIAN TABLES. 



218 



