M. Achille Cazin on Internal Work in Gases. 



91 



of the differences of level in the manometer Q corresponding to 

 those traces. Let H' be the difference of the final level which 

 corresponds to the pressure p', and H the difference observed at 

 a time t; the excess, positive or negative, H — H' = h is the ordi- 

 nate corresponding to the abscissa /. 



I shall show how a succession of values of p can be deduced 

 from the comparison of the various curves which we obtain by- 

 only changing the time comprised between the opening of the 

 stopcock C and that of the valve R, which time shall be denoted 

 by0. 



§ IV. Discussion of a series of experiments. How the pressure 

 varies during the expansion. 



Experiments of the same series are those in which nearly the 

 same values for p 1 and p 2 were preserved, and in which the value 

 of the interval of time 0, comprised between the opening of the 

 large stopcock C and that of the valve E, was alone changed. 



In reality the curve constructed for each experiment varies 

 with p l and p 2 for the same value of 6. But as the ordinates 

 only represent the excess h of the difference of the variable level 

 H over the final difference H', small changes in the values of p x . 

 p% produce no appreciable effect ; which dispenses with a reduc- 

 tion to constant values of p } , p r 



The following is a series made with dry air. The liquid in 

 the manometer Q was sulphuric acid. The values of h are mea- 

 sured by the heights of the liquid, calculated in millimetres. 



Series I. (November 1867). 

 Dry air. Metal Reservoir B. 

 ^ 1 =3*84 atmospheres, ^ 2 =0'22 atmosphere. Temperature 

 between 7° and 11°. 



Curves. 





















,{ 



= Os-5 



t=z-\ 



77 



14-6 



20-8 



37 



57 





120 



A= + 13 mm 



-136 



-42 



+ 10 



+ 16 



+ 10 



+6 









M 



= 0-7 



27 



6-8 



117 



16-3 



227 



34 



47 



120 



h =+30 



-108 



-20 



+20 



+25 



+20 



+ 10 



+5 







c -{ 



= 11 





75 



132 



17*3 



28-5 



37 



54 



120 



A=+29 



-126 



-35 



+ 19 



+25 



+ 14 



+9 



+4 







M 



= 3 



4-9 



9 



139 



17-5 



232 



35 



47 



120 



A =+22 



-54 







+ 25 



+26 



+20 



+ 10 



+5 







M 



= 36 



5 2 



9-5 



141 



17 3 



20-9 



29 



46 



120 



h=-\ 



-41 



+7 



+27 



+30 



+27 



+ 17 



+7 







M 



= 4 



5-4 



8-9 



114 



15 



19 9 22-8 



42 



120 



h=-l 



-25 



+ 12 



+27 



+32 



+27+22 



+7 







M 



= 4-1 



5-6 



10 



13-5 



166 



21-2 29-3 



39 



120 



A =+25 



-2 



+30 



+ 34 



+30 



+ 20+10 



+5 







H.{ 



= 4-3 



57 



10 



137 



19-6 



261 



39 



54 



120 



A=+12 



— 7 



+27 



+35 



+27 



+ 17 



+7 



+2 







M 



= 5 



8-6 



109 



137 



18-6 



22-9 32 



41 



120 



h=-7 



+ 17 



+ 28 



+32 



+27 



+22+12 



i 



+ 7 







