Correction of the Gas- Thermometer. 



91 



by his formula for air. For nitrogen, if we simply adopt the 

 values of the constants given for air, we find that thev satisfy 

 the observations of the compressibility at low temperatures, 

 and of the pressure-coefficient (0°* — 100° C.) rather better 

 than those given by Hose-Innes, which depend on the very 

 doubtful observations of the cooling-effect. 



Nitrogen. — Although we should probably be well within 

 the limits of experimental error in taking the corrections for 

 nitrogen to be the same as those for air, I have thought it 

 worth while to calculate the values of the constants for 

 nitrogen from ChappmV pressure-coefficient at 100 cms., 

 assuming # = 273°*10. This gives c = l:58 c. c. Whence 

 if c—b at 0° C. = 0*41 c. c, we have 6 = 1*14 c. c. Chappuis' 

 observations of the compressibility at 0° C. give c — 6 = 0*35 

 c. c, which would make 6 = 1*23 c. c. The volume of the 

 liquid at its boiling-point is 1*26 c. c, but this is probably 

 too large, so I have taken 6 = 1*14. The corrections calcu- 

 lated with these values are seen to be practically the same as 

 for air. 



Hydrogen. — In calculating the values of the constants for 

 hydrogen on the assumption 72=1*5, I have taken Chappuis* 

 value of the slope of the isothermals at 0°C., namely, 

 c — 6= —6*5 c. c, which is in close agreement with Regnault's 

 values, 5*5 to 6'6 c. c. at 4°C. Adopting also Joule and 

 Thomson's value of the heating-effect at 0° C, namely 

 Q = '0293° per atmo, we have c =l*50 c. c, 6 = 8*0 c. c. 

 The lvalue of 6 is slightly smaller than Amagat's limiting 

 volume 8*7 c. c. at high pressures, and much smaller than 

 the volume of the liquid 14 c. c, but it appears that hydrogen 

 is much more compressible than other gases or liquids under 

 these conditions. 



Table XII. 

 Values of Constants assumed for Diatomic Gases. 



Gas 

 employed. 



c. c. 



b. 

 c. c. 



c -b. 

 c. c. 



—6 



xio . 



S. 

 -6 



xio . 



1005 

 10-38 

 145-3 



Factor 



1 



c oPo/ R - 



76 cms. 



100 cms. 



Air 



1-48 

 1'5S 

 1-50 



0-98 

 1-14 

 8-00 



0-50 



044 



-6-50 



2-872 

 2-966 

 41-5 



0-516 



0-540 



0-0367 



0-678 

 0-710 



00482 



Nitrogen . . . 

 Hydrogen ... 



The value of the Absolute Zero O =273°\1OI is deduced 

 from the pressure-coefficient of hydrogen, and the pressure- 



