354 



Mr. J. Rose-Innes and Dr. S. Young on th 



te 



but at intermediate volumes they were somewhat greater, and, 

 as they exhibited considerable regularity, it is a question 

 whether they could be attributed entirely to errors of experi- 

 ment. In any case, the relation may be accepted as a close 

 approximation to the truth. 



A quantity of pure normal pentane having been obtained 

 by the fractional distillation of the light distillate from 

 American petroleum, it was decided to carry out a similar 

 investigation with this substance; but, as it had been found 

 that isopentane vapour at the largest volumes behaves 

 practically as a normal gas, it was not considered necessary 

 to make the determinations through so wide a range of 

 volume. 



The method employed for the separation of the normal 

 pentane from petroleum has been fully described in the Trans. 

 Chem. Soc. 1897, Ixxi. p. 442 ; and the vapour-pressures, 

 specific volumes as liquid and saturated vapour, and critical 

 constants have been given in the same journal (p. 44G). 



The data for the isothermals of normal pentane were 

 obtained by precisely the same experimental methods as in 

 the case of isopentane, and reference need, therefore, only be 

 made to the previous paper (loc. cit.) . 



There were four series of determinations ; and particulars as 

 to the mass of pentane, and the data obtained in each series 

 are given below : — 



Series. 



Mass of 

 [Xormal Pentane. 



Data obtained. 



I. 

 11. 



III. 



i IV. 



gram. 

 •10922 



•02294 



•005858 

 •001845 



Volumes of liquid to critical point ; volumes above 

 critical temperature to 280°. 



Volumes of unsaturated vapour from 140° to critical 

 point ; volumes above critical point to 280°. 



Volumes of vapour at and above 80°. 



Volumes of vapour at and above 40°. 



The correction for the vapour-pressure of mercury was 

 made in the same way as with isopentane : when liquid was 

 present it was assumed that the mercury vapour exerted no 

 pressure ; in Series I., above the critical point, one-fourth 

 of the maximum vapour-pressure of mercury was subtracted; 

 in Series IT. one-half ; in Series III. three-fourths ; and in 

 Series IY. the full pressure. 



The volumes of a gram of liquid and unsaturated vapour 

 are given in the following table. 



