216 



Mr. William Sutherland on the 



critical volume we have the behaviour of ethyl oxide repre- 

 sented by the simple form of equation 



pv=UT(l + -^_-L with £ = 4-066 and /=5514, 





+ *, 



involving only the two constants k and I peculiar to ethyl 

 oxide. 



We will now compare a few values of the pressures, in 

 metres of mercury, given by this equation with those found 

 by Ramsay and Young. 



Table II. 





Volume ... 



100. 



50. 



20. 



10. 



6. 



17^o n / Pressure, experiment. 

 [ Pressure, calculated. 



3-500 

 3538 



6-620 

 6-634 



1388 

 1378 







■jnxo p f Pressure, experiment. 

 [ Pressure, calculated. 



3-710 

 3719 



7-020 

 7021 



15 06 

 14-90 



2300 

 22-99 



27-00 

 27-44 



280° -f P ressure > experiment. 

 \ Pressure, calculated. 







19-80 

 19-69 



34-59 

 31-28 



49-62 

 49-00 



The agreement is as close as can be looked for ; because 

 although Ramsay and Young measure volumes to within 

 •01 centim., and pressures to within 2 centim. of mercury, the 

 quantities measured cannot be considered known with that 

 degree of accuracy; for the discrepancies between their mea- 

 surements and those of Perot (Ann. de Chim. et de Phys. 

 ser. 6, t. xiii.), who made special determinations in a large 

 globe of the saturation-volume of ethyl oxide at different 

 temperatures, are greater than those in Table II. Accord- 

 ingly it would be useless to seek a better empirical represen- 

 tation of Ramsay and Young's results than the above ; and 

 as we are chiefly interested in establishing our simple form of 

 characteristic equation, w T e had better proceed at once to the 

 consideration of Amagat's experiments on carbonic dioxide, 

 practically identical with Andrews's, but more extensive. 

 Amagat's unit of volume is 34V0 of that occupied by the gas 

 at 0° and 1 atmosphere ; taking the weight of a litre of the 

 gas at 0° and 1 atmosphere as 1 # 9777 gramme, we can 

 convert Amagat's data to the gramme and centim. as units. 

 The following Table is arranged in the same way as 

 Table I. :— 



