384 Scientific Proceedings, Royal Dublin Society. ■ 



hexamethyl ethane is therefore formed by the action of sodium on the 



bromide ; but it is completely removed during the fractional distillation. A 



small quantity was isolated in the form of volatile colourless crystals. 



Specific gravity at 074°, . . . 0-71021 



Boiling-point under normal pressure, . 109'2° 



The electrolytic method was found to give fairly satisfactory results ; but 

 as a sufficient quantity of di-isobutyl had been prepared already by the first 

 method, it was not considered necessary to purify the isovaleric acid by 

 fractional distillation. About 20 grams of di-isobutyl boiling from 109-15° 

 to 109'25° was obtained; but this specimen was not employed for the 

 determination of the physical constants. The first specimen of di-isobutyl 

 appeared to be quite pure ; the boiling-point was constant ; and the specific 

 gravities of the two fractions agreed very well together. The vapour-pressure 

 also at each temperature remained quite constant when the relative volumes 

 of liquid and saturated vapour were altered. It has, however, been pointed 

 out by Dr. Mills that there are certain anomalies in some of the physical 

 constants for this substance ; and it is a remarkable fact that after being kept 

 for two or three years in well-corked bottles, both specimens had evidently 

 undergone some change, for a few colourless crystals were present in each, 

 and the quantity of the crystalline deposit has continued very slowly to 

 increase, but is still hardly large enough to allow of a satisfactory investiga- 

 tion of the chemical nature of the substance. It seems just possible that 

 the di-isobutyl may have already contained a minute amount of this impurity 

 when its physical properties were determined. 



8. Hexaniethylene^ — A small quantity of this substance was obtained by 

 Miss E. 0. Fortey by the long-eontiuued fractional distillation of Galician 

 petroleum. It boiled quite constantly at 80'8°, and its specific gravity at 

 0°/4°, 07903, agreed perfectly with that of a specimen prepared synthe- 

 tically by MarkownikofE.^ It was found that it solidified partially in a 

 freezing mixture, but that the freezing-point was very far from constant 

 (about - 12° to - 7°) ; and it was evident that it contained a certain amount 

 of another hydrocarbon, probably a heptane such as tri-methyl propyl 

 methane, boiling at a temperature near to 81°, and inseparable from tiie 

 hexamethylene by fractional distillation. Fractional crystallization was 

 therefore resorted to ; and the less pure fractions (76° to 78'5°J, left over after 

 the chemical investigation, were utilized in addition to the small quantity of 

 material of constant boiling-point. 



Special methods of separation of the crystals from the mother liquor were 



' Fovtey and Young, Trans. Chem. Soc, Ixxv., p. 873, 1899. - Annalen, cccii., p. 1, 1898. 



