382 Scientific Proceedings, Royal Dnhlin Society. 



respects similar to that of Dormal hexane, except that a more efficient still- 

 head was employed. The distillate, which came over at a constant tempera- 

 ture, was collected in three fractions. 



Specific gravity at 074°, . . . . A == 0-71850 



„ . . . . 5 = 0-71847 



„ . . . . 0=0-71848 



Later determination with new tube, . . 0-71854 



Boiling-point under normal pressure 125-8". 



5. Isopentane^. — Three specimens of this paraffin were obtained from 

 different sources : — 



(«) Erom Kahlbaum's "pentane," This substance is obtained as a by- 

 product in the preparation of amylene from amyl alcohol, the admixed amyl- 

 ene being for the most part separated by means of bromine. The method of 

 purification was similar to that employed for normal pentane ; but after 

 treatment with the mixed acids, and before that with caustic potash, the 

 liquid was repeatedly shaken with concentrated sulphuric acid until no further 

 orange coloration was noticeable. After complete removal of amylene by 

 the acids, pure isopentane is easily obtained by fractional distillation. 



(J) From amyl iodide. The strongest possible hydrochloric acid was 

 added drop by drop to amyl iodide, dissolved in five times its volume of absolute 

 alcohol, in presence of zinc on which a little copper had been deposited. The 

 temperature was maintained at 0°, and the action was complete in about twenty- 

 four hours. The liquid was poured off and distilled from the water-bath 

 until no more isoptane came over ; the distillate was shaken with water 

 several times to remove alcohol ; bromine was added, to remove amylene, 

 until the isopentane was permanently coloured ; excess of bromine was 

 removed by adding caustic potash; and the isopentane was then washed 

 with water, dried with calcium chloride, and fractionally distilled. 



(c) From American petroleum. The separation of the two peutanes from 

 petroleum has been described under normal pentane. 



The three specimens boiled constantly at 27-96° under normal pressure. 

 Their specific gravities at 0'^/4° were found to be : — 



(«) {b) (c) 



1. 0-63925 0-63935 1. 0-63931 



2. 0-63922 2. 0-63929 



6. JDi-isoproppl.^ — Great difficulty was experienced in tlie preparation of 



1 Proc. Phys. Soc, xiii., pp. 602, 658, and 666, 1895, and Zeitschr. physik Chem., xxix., p. 193, 

 1899; Trans. Chem. Soc, Ixxi., p. 440, 1897. 



2 Fortey and Young, Trans. Chem. Soc., Ixxvii., p. 1126, 1900. 



