180 Mr. W. Sutherland on the 



Regnault's data by the equation 



K p =426(-187 + -00027*). 



Cooling-effects experienced by C0 2 when escaping at different 

 temperatures through a porous plug into the atmosphere 

 under an excess of pressure of 2*54 metres of mercury. 



Temperature 



7°-38. 



7° -96. 



19°-1. 



35°-6. 



54°. 



91°-5. 



93°-5. 



97°-5. 



Observed by Thomson "1 

 and Joule J 



4-367 

 3-940 



4-215 

 3-920 



3-876 II. 

 3-670 



3-407 

 3-330 



2-951 

 3-010 



2-348 II. 



2470 



2-164 

 2-453 



2-135 



2-395 



Calculated from equation 



When the great difficulty of these experiments with porous 

 plugs is considered (they baffled Regnault himself, " Sur la 

 detente des Gaz/' p. 707), the agreement between the calcu- 

 lated and observed cooling-effects will be seen to be satis- 

 factory. Regnault, while unable to get satisfactory results 

 by the porous-plug method, obtained some valuable data by 

 allowing gases to expand through a fine hole in a thin wall 

 into a calorimeter, and also by allowing them to expand 

 through silver capillary tubes of different lengths. As the 

 excess of pressure which he employed was on the whole 

 greater than the average excess in Thomson and Joule's 

 experiments, and was such that we can no longer consider 



as proportional to pi—p 2 y I have applied Thomson's 



equation for the cooling-effect to the actual circumstances of 

 each of Regnault's experiments. 



Cooling-effects experienced by C0 2 in escaping at different 

 temperatures into the atmosphere under different pressure- 

 excesses. 



Temperature at 

 the high pressure. 



Excess of pressure, 

 in millim. 

 of mercury. 



Observed 

 by Begnault. 



Calculated 

 from equation. 



-25 C. 



7541 



18-73 



15-30 



3 

 3 



3354 

 7764 



5-43 

 12-73 



5-50 

 12-93 



15 



38591 



81-96 



73-80 



100 

 100 



4682 

 7921 



4-72 

 9-88 



4-34 

 7'30 



