Thermal Properties of Normal Pentane. 



365 



to volumes lying above 3*4 ; and this limitation still leaves us 

 with all those conditions of the substance in which we can 

 most usefully compare it with isopentane. 



Looking at the table on p. 362, which gives the series of 



values of — # an( * comparing it with the similar table for 



isopentane (Proc. Phys. Soc. xiii. pp. 654, 655), we notice 



that at the same volume the value of — t, is always smaller in 



the former case than in the latter. The difference is not great, 

 but it remains too persistently with the same sign for us to 

 disregard it. As we proceed to larger and larger volumes, 

 however, the difference diminishes on the whole, and an 

 interesting question arises whether we should be justified in 

 treating it as ultimately vanishing when v is made infinite. 





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To elucidate this point a diagram was drawn in which the 



differences of — ^ between isopentane and normal pentane 



were plotted against v~* ; this diagram is reproduced 

 above. The diminution in the differences with increase of 

 volume is well shown in spite of the " wobbling " at large 

 Phil. Mag. S. 5. Vol. 47. No. 287. April 1899. 2 G 



