M. Achille Cazin on Internal Work in Gases. 



203 



is greater than that of zinc. As the heat finally taken from the 

 sides by the total mass of the gas is less with glass, we also 

 see why the curve of the h's rises less quickly in this case than 

 in the other. It is evident that, in order to know exactly the 

 influence of the nature of the sides, we ought to operate with 

 reservoirs of the same form and size; but the foregoing is suffi- 

 cient to prove the small importance of this research, and I have 

 not considered it necessary to undertake it. 



§ XL Influence of the initial pressure of the compressed gas. 



When the pressure p l is changed, and consequently the pres- 

 sure p 2 , since the final pressure p' does not change, the curve of 

 the h's is greatly modified. The following series lead to the law 

 which governs these modifications. I shall first mention two 

 series performed on carbonic acid, which present a very complete 

 example. 



Series IX. (November 1867). 

 Dry carbonic acid. Metal reservoir B. 



jDj = 3*80 atmospheres, j? 2 = 0*22 atmosphere. Temperature 

 between 5° and 8°. 



(0=0-13 



t=2-7 



4-4 



7 



10 



12-2 



17 



27 



34 







120 



-133 



-80 



-28 



+3 



+ 13 



+21 



+ 13 



+ 11 











R f 0=0-26 

 D '\A = +53 



2-9 



57 



8-1 



104 



131 



176 



22 



25 



36 



45 



120 



-112 



-61 



-29 



-8 



+7 



+ 17 



+ 19 



+ 17 



+ 12 



+ 8 







MK-1 



3-8 



6-8 



8-9 



10-6 



13-2 



16-2 



19-4 



25 



37 



46 



120 



-136 



-83 



-50 



-31 



-10 



+ 5 



+15 



+ 18 



+ 15 



+ 10 







Mfc-t. 



5-8 







10-3 



13-5 



18-6 





23-3 



31 



39 



120 



-35 







+ 2 



+ 17 



+25 





+22 



+ 17 



+ 12 







L '\A=+20 





7-1 







12 



18-6 





27'4 



34 



41 



120 





-14 





... 



+ 14 



+30 





+24 



+ 19 



+ 14 







H e aU 





6-6 





11 



142 



17 



2*i*2 



241 



30 



39 



120 





-24 





+5 



+20 



+ 25 



+28 



+25 



+20 



+ 13 



r r 0=5-i 

 G 'U=+io 



. • • 



6-7 





11 2 





175 



24-4 



29-2 



34 



40 120 



... 



-13 



... 



+ 10 





+30 



+25 



+20 



+ 15 



+ 10j 



„ J 0=5-2 

 U '\h= +2 





73 



... 



12-2 





172 



21-9 







40 120 





-18 





+ 13 





+24 



+20 





::: 



+ 13| 



The curves of this series have been traced in fig. 7; and the 

 line X X was obtained by following the general rule given in 

 § IV. It represents the actual variable pressure deduced from 

 the observed variation of the manometric level. It cuts the axis 

 of the abscissae in the point x = 9 seconds \ and its maximum cor- 

 responds to ?/=+30 millims., # = 18 seconds. The greatest 

 depression of h, for the curve C, occurs where h= —136 millims. 

 (sulphuric acid). 



We must notice the first curve, A, which remains below XX. 

 Tt represents an experiment in which the level of the manometer 

 was very low at the moment the valve was opened. We see that 



P2 



