198 



M. Achille Cazin on Internal Work in Gases. 



its sides, this depression would disappear as rapidly as the 

 mist. Thus we should not observe the effect described ; but the 

 presence of aqueous vapour would exercise a considerable influ- 

 ence on the magnitude of the depression. Hence the objection 

 is important, and it was indispensable to be certain that the gas 

 was completely dried. 



For this purpose 2 metres of pumice-stone saturated with sul- 

 phuric acid were placed between the tubulures H and H'; and 

 after having compressed the gas in A by means of the pump, it 

 was allowed to return to the reservoir B, passing through the long 

 Column of pumice-stone as slowly as was wished : it was sufficient 

 to regulate properly the stopcocks r', r" 1 (fig. 2). This manipu- 

 lation was repeated several times before Series VII. (on hydrogen) 

 was commenced; and it was ascertained that no appreciable 

 moisture was deposited in a drying-tube, by weighing the latter 

 before and after the passage of the gas. Experiments A, B, C, 

 D of the following series were then made ; the minimum of h 

 was between —90 millims. (sulphuric acid) and —102 mil- 

 lims. After this trial a column of anhydrous phosphoric acid of 

 60 centims. was placed between the tubulures H and H/, and 

 the gas was made to pass several times through this sub- 

 stance by the process described. The two experiments « and ft 

 were then made, and the minimum of h was —108 millims. and 

 — 89 millims. The six curves of this series are identical, so that 

 it is impossible to admit the influence of moisture. Hence the 

 drying by sulphuric acid is sufficient. In all the experiments 

 the gas was not only dried during its introduction into the reser* 

 voirs, but also afterwards by the process described in the present 

 paragraph. 



Series VII. (September 1867). 



Dry hydrogen. Metal reservoir B. 



j9j = 3-80 atmospheres, p 2 = 0*22 atmosphere. Temperature 

 between 20°-7 and 21°'2. 



r 0=0-12 



#' \ h=-2 mm 



t-^2-2 



45 



72 



107 



191 



24 



54 



60 



-102 



-45 



-3 



+ 12 



+7 



+5 



+ 1 







n re=o-i2 

 B \h=-\ 



21 



57 



77 



101 



138 



18-3 



24 



60 



-100 



-25 



-4 



+6 



+9 



+6 



+ 4 







r re=o-4i 



c - \h=0 



2-4 



4-5 



6 



81 



12 



161 



24 



60 



— 92 



-45 



-13 



+7 



+ 16 



+ 12 



+7 







D [6=0-57 



2 8 



57 



8-3 



11-8 



175 



... 



24 



60 



-90 



-21 



+ 10 



+ 18 



+ 10 





+5 







{9=0-23 



2-4 



51 



6-8 



10-5 



13-9 



17*6 



23 



60 



"' U = + 12 



-108 



-30 



-M 



+ 20 



+ 16 



+ 11 



+ 6 







a / 6= 0-91 



29 



5-4 



7-2 



9 



10-9 



13-4 



23 



60 



-89 



-28 



+3 



+ 18 



+22 



+ 18 



+6 







