538 



SCIENCE. 



[N. S. Vol. IV, No. 93. 



From these results it may be concluded that 

 the molecules of liquid isopentane are simple, 

 like those of the gas. 



Specific Volumes of Isopentane Vapor at low Pres- 

 sures. By Sydney Young, D. Sc, F. R. S., 

 and G. L. Thomas, B. Sc. , University College, 

 Bristol. (Physical Society of London.) 

 The specific volumes at low pressures were 

 determined in a Hofmann's apparatus, modified 

 in such a manner that the volume as well as 

 the temperature could be altered at will. This 

 apparatus was first employed by Ramsay and 

 Young (Phil. Trans. 1887 A. 58), but various 

 improvements have been introduced, and are 

 fully described in this paper. 

 Isopentane from Amyl Iodide. By the same 

 authors. (Physical Society of London.) 

 A specimen of isopentane was prepared by 

 the action of very concentrated hydrochloric 

 acid (added drop by drop very slowly) and zinc 

 slightly coated with copper on an ice-cold 

 alcoholic solution of amyl iodide. The isopen- 

 tane was purified by treatment with bromine 

 and subsequent fractional distillation. 



Determinations were made of the boiling 

 point, specific gravity at 0°, the critical tem- 

 perature and pressure and of the vapor pres- 

 sures and specific volumes of liquid and satu- 

 rated vapor at a few temperatures. 



The boiling points, specific gravities and 

 critical constants of both specimens of isopen- 

 tane are given below : 



Isopentane Isopentane from 



from Amylene. Amyl Iodide. 



Boiling point (mean) 27.95° 27.95° 



Specific gravity at 0° 0. 63924 0. 63935 



Critical temperature 187.8° 187.8° 



Critical pressure 25010 mm. 25030 mm, 



Critical volume of a gram..4.266 cb. cms. 



The Vapour Pressures, Specific Volumes and Criti- 

 cal Constants of Normal Hexane. By the same 

 authors. (Communicated to the Chemical So- 

 ciety of London.) 



The normal hexane employed in this investiga- 

 tion was obtained from Kahlbaumit; it had been 

 prepared by the action of sodium on propyl 

 iodide. It was purified by treatment with 

 mixed sulphuric and nitric acids and by subse- 

 quent fractional distillation. 



The vapor pressures and the volumes of a 



gram of liquid and saturated vapor were deter- 

 mined at a series of temperatures, and the ratio 

 of the absolute temperatures (boiling points) and 

 the volumes to the critical constants were cal- 

 culated at a series of pressures ' corresponding ' 

 to those previously adopted. 



Like isopentane, normal hexane was found 

 to belong to group I, and the molecules of liquid 

 in this case also are probably simple like those 

 of the gas. The ratio of the actual to the theo- 

 retical density at the critical point is 3.83. 



As regards the comparison with isopentane^ 

 it is noticed that the absolute temperature 

 ratios at ' corresponding ' pressures are higher 

 for the parafiin of higher molecular weight, and 

 in this respect the parafl&ns seem to resemble 

 the esters (Trans. Chem. Soc. 63, 1252), for 

 which the ratios increase without exception 

 with rise of molecular weight. 



In the case of the esters the volume ratios ap- 

 pear to be independent of molecular weighty 

 but, for isomeric compounds, to depend to some 

 extent on the constitution. It seems probable 

 that this may also be the case for the two par- 

 affins studied, but an investigation of other 

 paraffins will be necessary before these points 

 can be decided. 



The relations of pressure to temperature 

 at constant volume were investigated through a 

 small range of volume (from 9 to 83 cub. cms, 

 per gram ; critical volume = 4.268 cub. cms.)^ 

 and it was found that with hexane as with iso- 

 pentane the values of —r- at these volumes di- 

 dt 



minish slightly on rise of temperature. 



Normal Hexane from Petroleum Ether. By the 

 same authors. (Chemical Society of London.) 

 An attempt was made to obtain a pure hex- 

 ane from ' petroleum ether ' by fractional dis- 

 tillation by the method employed by the authors- 

 in the separation of ethyl acetate from a mix- 

 ture of methyl, ethyl and propyl acetates (Phil. 

 Mag. Jan. 7, 1894, 8). A dephlegmator 125. 

 cms. in length, with twelve constrictions (Chem. 

 News, 77, 177) was employed. 



Each fraction was weighed and its tempera- 

 ture range noted and corrected for the thermo- 

 metric error and for the difference between the 

 barometric reading and 760 millims. The ratio 

 of the Ayeight of any fraction (A^) to its. 



