of Vapours to Mario'tte and Gay-Lussac's Lc 



297 



with certainty at6I 0, 8 arc those given in Tabic II. But by the 

 help of one approximately estimated maximum tension, which is 

 taken from the relation of the remaining maximum tensions to 

 those of Regnault* (touching which I may remark that the 

 difference between the two is greatly affected by the difference 

 in the preparations), the probably correct value of v i may be 

 calculated, since with a small value of v L and a high value of p x a 

 mistake in the latter to the amount of a few millimetres would 

 alter the value of v x only very little. 



Table II. a. 



Temperature £ 



30°-4 



39°-8 



49°-8 



64^-8 





Mean of the observed PV... 



Mean PV corrected for 1 

 the mean vapour-den- I 

 sity 4-189 J 



21923 

 21928 



1-03614 



21164 



24308 

 87-1 



22590 



22602 



1-05209 



21483 



354-77 

 60-6 



23313 

 23313 



1-06881 



21812 



51407 

 424 



24434 



24399 



109331 



22317 



870 nearly 

 25-7 



0-0595 */J+t(=—) 



p x v x calculated from this by "1 



the aid of PV corrected J 



p lt mean of the observations. 



v± calculated from this 



Table II. b. 





30°-4. 



39°-8. 



49°-S. 





Extreme limits x < 



Corresponding c in the "] 



PV , I 



ratio =cya-\-t ... 



P\ v i J 



87-1 

 88-5 



0-05949 

 0-05858 



60-5 

 61-5 



005961 

 005864 



421 



43 



005997 

 0-05871 



A survey of these Tables shows how closely the assumption 



PV . 



= 0*0595 Va-\-t harmonizes with the observations. Hence 



also for alcohol and chloroform the same temperature (9°'5) must 

 exist at which the vapours of both fluids, so soon as they pass 

 from a fluid state, follow Mariotte's law - the point of maximum 

 tension (very different at 9 0, 5) appears to have no influence on 

 the position of this temperature. 



§ 6. Examination of the Vapour of Bisulphide of Carbon. 



To prove perhaps the universal validity of this remarkable 

 phenomenon, there was taken for the third body bisulphide of 

 carbon, the maximum tension of which at 9°*5 is considerably 

 greater than that of chloroform. This body, having been pre- 

 pared so as to be quite pure, was protected from the light during 

 the investigation by a piece of yellow glass. The following Table 

 gives the simultaneous v and p for five temperatures, and there- 

 with the respective products pv. 



* Mem. de V 'Acad, des Sciences, vol. xxvi. p. 403. 



Phil. Mag. S. 4. Vol. 38. No. 255. Oct. 1869. X 



