﻿Volume, and Temperature of Rarefied Gases, 303 



individual readings, were made with air ; the diminution of 

 pressure varied in these series from that of the atmosphere to 

 1*4 millim. ; and by means of an accurate cathetometer the 

 pressure was read to the second decimal place. The ratio of 

 V (the volume of the closed reservoir) to V + V (that of both 

 reservoirs) was calculated by means of the formula 



_ E(V + np) _ eV> 



lj -y+yi+nff* v+v+wy 



where 



E is the original pressure of the gas ; 



e, pressure read on gauge of second cylinder or of air-pump 



after exhausting ; 

 E', pressure in cylinders after opening the stopcock ; 

 rifM and n'fi, small corrections introduced, due to alteration 



in total volume of apparatus owing to rise of mercury in 



the gauges, n is a number of centimetres, \x the capacity 



of one centim. of the gauge. 



ft (in following equation) = fi/V. Hence 



V'_ E(l+n/3)-E (1 + w'fl) 

 V ~ E'-tf 



If the ratio (V + V')/V remains constant, Boyle's law holds ; 

 if, on the contrary, (V + V)/V be too great or too small, the 

 pressure E' would be either less or greater than corresponds 

 with Boyle's law. 



The results were averaged, series a and b being compared 

 with series c and d ; the latter with series e and/, and so on. 

 This process yielded six sets of average values of (V + Y f )/V 

 for air. The results follow : — 



Extremes 



of pressure. 



v+vyv. 



759 and 



352 millim. . 



. 1-47209 



352 „ 



164 



?? • 



. 1-47165 



164 „ 



77 



j? 



. 1-46887 



77 „ 



37 



V 



. 1-46870 



37 „ 



18 



}' • 



. 1-46122 



18 „ 



7 



5? 



. 1-46511 



These values of V + V'/V decrease with falling pressure ; 

 the higher its value the lower the value of E', and vice versa. 

 Assuming from Eegnault's observations between 1 and 30 

 atmospheres that at a pressure of 1 atmosphere the value given 

 above, 1*4720;', is correct, and that Boyle's law holds under 

 such a pressure, it follows that the pv of the air increases 

 with decreased pressure. This conclusion, too, Siljestrom 



