132 



M. V. Regnault on the Expansion of Gases. 



worm fits somewhat tightly in the tubulure of the first tube A ; 

 the junction is hermetically cemented. 



When the stopcock of the large reservoir is opened, the 

 gas circulates in the worm, retaining almost the same pressure 

 as in the reservoir, but acquiring the temperature of the water 

 of the bath. This pressure is in like manner transmitted to the 

 first tube A of the calorimeter ; expansion only commences as 

 the gas emerges from the capillary orifice of the first tube A. 

 A second expansion takes place as the gas passes through the 

 second capillary orifice, so that the elastic force of the gas is less 

 in the tube C than in the tube B. On emerging from each of 

 the vertical tubes, there is au expansion, until the gas reaches the 

 twelfth and last tube, where it is virtually under the pressure of 

 the atmosphere. 



The capillary apertures which the gas thus successively tra- 

 verses have gradually larger diameters as they become more dis- 

 tant from the orifice, in order that the relative value of the ex- 

 pansion may be nearly the same for each orifice, notwithstanding 

 the successive variation which the pressure experiences in each 

 vertical tube. 



The experiment is otherwise made in exactly the same manner 

 as when the calorimeter was used with superposed boxes and 

 a single expansion. 



Experiments made by means of the calorimeter with successive 

 expansions gave the following values of y l (that is to say, the 

 lowering of temperature experienced by the gas for a diminution 

 in pressure of 1 metre of mercury) :— 



Mean excess of 

 pressure. 



Weight of air 



escaped in a 



minute. 



fv 



Vv 



millimetres. 

 4780 

 6080 

 7421 

 6607 

 6314 

 5763 



grammes. 

 34-5 

 440 

 50-3 

 8-9 

 13-6 

 37-2 



metre. 

 1-000 



»> 



»» 

 >> 



0-3590 

 0-3290 

 0-3580 

 0-3781 

 0-3621 

 0-3426 







Mean of 3^= -0-3548 



The last three experiments were made under almost the same 

 pressure, but with very different velocities of outflow. They show 

 that the value of y Y is greater the less the velocity of the ex- 

 panded gas on its emergence from the calorimeter. I give the 

 reason for this in my memoir. 



In order that the results of various experiments may be per- 



