of Vapours to Mariotfce and Gay-Lussac's Law. 299 



The size of the air-bubble was -325 cubic centim. at 0° and 760 

 milliins. pressure; the weight of the bisulphide of carbon was 

 "0717 grm. The final vapour-densities calculated therefrom 

 agree with one another very well, as the following comparison 

 shows : — 



Temperature 



8° -5 



14°-2 



20°-l 



32° 



35°-9 



Vapour-density ... 



2-686 



2-683 



2-682 



2-680 



2-680 



Their deviation from the theoretical vapour-densities has been 



PV 



mentioned above. The relation — ~=c Va + t is exhibited with 



P\ v \ 



the same constant, c = *0595, in fact confirmed here also, as 



a comparison of the following Tables with the corresponding 



preceding one shows : — 



Table III. a. 



Temperature t 



8°-5 



14°-2 



20°1 



32° 



35° -9 





Mean of the observed PV ... 



Mean PV corrected for ] 

 the mean vapour-den- l 

 sity 2-682 J 



16175 

 16199 



1 



16199 



18309 



88-5 



16521 

 16528 



1-00813 



16385 



234-45 



69-9 



16867 

 16867 



101842 



16562 



294-12 

 56-3 



17565 

 17552 



1-03888 



16895 



461-54 

 366 



17792 

 \7777 



104554 



17003 



531-59 

 32 



0-0595 V^+7/= —\ 



p x v | calculated from this by \ 



the aid of PV corrected J 



p v mean of the observations. 



»i calculated from this 





Table 



III. b. 









Temperature t 



8°-5 



14°-2 



20°1 



32° 



35° -9 





Extreme limits of v x 1 



Corresponding c in the "| 



ratio =cVa + t... \ 



Pi*i - J 



85 



88-5 



006204 

 0-05949 



69-2 

 70 



006012 

 005943 



56-2 

 57 



005961 

 0-05877 



34-7 

 37 



0-06204 

 0-05818 



31-4 

 32-5 



0-06057 

 005852 



The temperature 8°'5 was taken on a cold October day, yet 

 could not be maintained without the help of some ice. This 

 certainly influenced the degree of constancy in the temperature 

 which existed in all other cases. The numbers obtained are less 

 accurate ; but they appear to show pretty clearly that for these 

 temperatures the vapour already follows Mariotte's law imme- 

 diately on it3 declension from the point of maximum tension. 

 The differences of the four products, given in Table III., are some- 

 what irregular; but when we take into account the small fluc- 

 tuations of temperature which certainly did exist ; they may lie 

 quite within the errors of observation. 



X2 



