108 PROCEEDINGS OF THE AMERICAN ACADEMY. 



it was assumed that we had in hand the butane which Warren had pre- 

 viously separated. Suspecting, therefore, the purity of our hydrocarbon 

 distillate 8°-9°, in resuming this work the distillation was conducted 

 with a sufficient quantity of material, and carried far enough to separate 

 completely all fractions between 5° and 20°. In the fraction 8°-9°, 

 after the tenth distillation, two vapor density determinations gave, 

 (I.) 2.17, (II.) 2.17. In a distillate 6°-8°, Ronalds* obtained as its 

 vapor density 2.178, evidently indicating as our values do a mixture of 

 butane and pentane. 



But continuing this distillation in single degree fractions, scarcely any- 

 thing remained within these limits after the twentieth distillation. Hav- 

 ing obtained the same result in several quantities of forty-five litres 

 each, collet-ted at different dates, it became evident that neither Pennsyl- 

 vania nor Ohio petroleum contains a single body with a boiling point 

 between these limits. Furthermore, we have not been able to detect 

 normal butane in any of these volatile distillates. There is not the least 

 difficulty in separating chlorine derivatives of these hydrocarbons by 

 fractional distillation. All the chlorine products we have prepared have 

 collected readily within the limits of temperature of their characteristic 

 boiling points. But in no instance in the chlorination of hydrocarbon 

 distillates collected between — 10° and 20° has a distillate collected at 

 77°-78°, the boiling point of normal butyl chloride. Having excluded 

 a constituent of Pennsylvania and Ohio petroleum within the limits men- 

 tioned above, and having observed that certain properties of isopentane 

 derivatives are not in all respects identical with those previously published, 

 it seemed to us of sufficient interest to devote some attention to the deriva- 

 tives of this hydrocarbon. "We therefore collected several hundred grams 

 of a distillate at 29°-30°, and exposed the oil to the action of chlorine in 

 several separate quantities until about 200 c.c. of the substitution product 

 was obtained. In generating such large quantities of chlorine, without 

 discomfort from leaks, we have found the large Berlin porcelain stills 

 extremely convenient. The chlorinated product was washed, dried, and 

 carried through a long course of distillations, until after the eighteenth dis- 

 tillation it collected to the extent of 85 per cent between 95° and 96°, under 

 a constant tension of 730 mm., which for convenience was selected for all 

 these distillations. In a large series of distillations a constant tension is 

 simply and very conveniently obtained by means of the tension regulator 

 elsewhere described,! with the stopcock manipulated by a lever movable 



* These Proceedings, XXXI. 10. t Journ. Ch. Soc, 1865, p. 54. 



