380 Scientific Proceedings, Royal Dublin Society. 



•6. Ethjl Alcohol, E. and Y., ibid., elxxvii., Pt. 1, p. 123, 



4. Propyl Alcohol, R. and T., ibid., clxxx., p. 137, 1889. 



5. Acetic Acid, II. and T., Trans. Chem. Soc, xlix., p. 790, 1886. 



6. Isopentane, Young, Proc. Phys. Soc, xiii., pp. 602 and 658, 1895, and 



Zeitschr. physik. Chem., xxix., p. 193, 1899. 



7. Normal Pentane, Eose-Innes and Young, Phil. Mag. (5), xlvii., 



p. 353, 1899, also (5), xlviii., p. 213, 1899, and (6), ii., p. 208, 

 1901. 



8. Normal Hexane, Thomas and Young, Trans. Chem. Soc, Ixvii., p. 1071, 



1895. 



9. The vapour-pressures, specific volumes, and compressibilities of steam 

 from 120° to 270° have been determined by Eamsay and Young, Trans. Eoy. 

 Soc, clsxxiii.A, p. 107, 1892. 



Preparation of Material. 



The physical properties of a substance, more especially at or near its 

 critical point, may be seriously affected by the presence of even a very small 

 quantity of impurity ; it is therefore of the utmost importance that the 

 purification of the substances investigated should be carried out with the 

 greatest possible care. Full details of the methods of preparation and 

 purification of the thirty compounds are given in the original papers ; but it 

 may be useful here to state briefly the methods employed in each case. 



1. Normal Pentane.^ — This paraffin was separated from American 

 petroleum by fractional distillation through a combined dephlegmator and 

 " regulated temperature " still-head. The material from which the paraffin 

 was obtained was Merck's " pentane," a light distillate from petroleum 

 consisting chiefly of pentanes with relatively small quantities of butanes, 

 hexanes, pentamethylene, &c. 



After three preliminary fractionations, the distillates coming over 

 between about 28° and 37° (1030 grams) were shaken with («) concentrated 

 sulphuric acid, [b) mixtures of concentrated sulphuric and nitric acids, 

 (c) water, [d) caustic potash, and (e) water. They were then distilled over 

 phosphoric anhydride, and the fractional distillation was continued. The 

 weight of pure normal pentane obtained after twenty-one fractionations was 

 175 grams, 101 grams of pure isopentane being also separated. Each of 

 the parafiins was finally collected in two fractions ; and the specific gravities 

 were determined by means of a Sprengel tube of the form recommended by 

 Perkin. The weighings were in all cases corrected for the buoyancy of the 

 air. 



young and Thomas, Trans. Chem. Soc, Ixxi., pp. 440 and 446, 



