210 M. Achille Cazin on Internal Work in Gases. 



thereabouts, Hence the difference is still more marked than in 

 the preceding series. We also see from the Table of Series II. 

 that the initial depression is greater for hydrogen — which con- 

 firms a conclusion already given, because for this gas the velocities 

 of efflux are greatest. It is certainly convenient to make reser- 

 voir B of greater capacity than the zinc reservoir ; but the neces- 

 sity of keeping up a current of water around it makes me prefer 

 the latter in final experiments. 



§ XIII. Summary and conclusions of the experiments. 



All the observations above given may be summed up in the 

 following statement :— 



When a reservoir containing compressed gas is placed in com- 

 munication, by a large orifice, with a reservoir containing the 

 same gas rarefied, equality of pressure establishes itself very 

 quickly in the two reservoirs (0*1 second). When equality of 

 pressure commences, the velocities acquired have not completely 

 disappeared. At this instant there is a mechanical work pro- 

 duced in the first reservoir and a certain quantity of heat has 

 disappeared. There is, on the contrary, mechanical work ex- 

 pended in compression and heat created in the second reservoir ; 

 but a part only of the vires vivce produced during the efflux has 

 been transformed into heat. Whilst the velocities acquired con- 

 tinue to disappear in creating more heat, the pressure increases. 

 When all agitation has ceased, the heat which has disappeared 

 from the gas of the first reservoir remains greater than that which 

 has been created in the gas of the second reservoir. If the sides 

 were impermeable to heat, equilibrium of temperature would re- 

 establish itself by exchanges of heat between the cold and hot 

 parts, and the final temperature would be less than the initial. 

 As the sides are not impermeable to heat, those of the first reser- 

 voir give heat, those of the second take heat from the gas, and 

 finally there is an introduction of exterior heat, so that the ex- 

 changes between the cold and hot parts bring about a tempera- 

 ture greater than the initial temperature. 



One part of the heat introduced remains in the gas and re- 

 places the heat which has disappeared in the operation ; the rest 

 is retaken by the sides during the very slow cooling which re- 

 establishes the initial temperature. Hence, during the entire 

 operation, there is at the same time, change of distribution of heat 

 between the various portions of the sides, and destruction of a 

 certain quantity of heat, which is so much greater the more the 

 gas diverges from the laws of Mariotte and Gay-Lussac. It is 

 this latter quantity which is converted into internal work in 

 the gas, 



[To be continued.] 



