5io 



SCIENCE PROGRESS 



These observers determined the values of the product pv for 

 these gases from p b = 830 mm. to p a = 158 mm. Since it will 

 frequently be necessary in what follows to refer to diagrams in 

 which pv is plotted (as ordinate) against p (as abscissa), they 

 may be conveniently called compressibility diagrams. Gray 

 and Burt found that in the case of oxygen the compressibility 

 graph was a straight line whilst in that of hydrogen chloride a 

 slight but decided curvature was evident, the curve being con- 

 cave to the axes of co-ordinates as indicated in figs. 1 and 2. 

 The results for oxygen bear out what had been previously 



I Oatm 



\2-0ghn. 



Fi&£ 



known since the researches of Regnault on the subject, that 

 in the case of the difficultly liquefiable gases, pv may, with 

 sufficient accuracy, be regarded as a linear function of p for 

 pressures up to three or four atmospheres. Hence it is quite 

 simple to extrapolate to p = o for these gases. Algebraically, we 

 may say that A£ is a constant for values of p up to three or four; 

 and since in the case of these gases the numerical values of this 

 coefficient are very small and 



.A-o 1 *»-o-c; " *»-i • • * • 



P0V0 P.5V.5 P1V1 



we may regard either Al- 5 or A] as being practically identical 

 with A' 



