Yovm—Vymir-P-rcssures, §'c., of Thirty Pure Subatances. 381 



Specific gravity of normal pentane at 074° , A = 0-64536 

 :, • . B = 0-64541 



BoiliBg-point under normal pressure . . 36-3° 



Another specimen of normal pentane, recently separated from "petroleum 

 ether" by fractional distillation through an "evaporator" still-head of 

 fifteen sections, after treatment with acids, &c., as above, had the same 

 specific gravity ; but the boiling-point appeared to be a little lower. The 

 difference is doubtless due to an error in one of the thermometers; and 

 it may be mentioned that the zero points of the German soda-glass 

 tliermometers originally used were not quite constant. The boiling-point 

 calculated by means of Biot's formula is 36'13°. 



2. Normal Hexane}~T\xe speoijueu employed for the chief determinations 

 was obtained from Kahlbaum, and had been prepared by the action of 

 sodium on propyl iodide. It was treated with acids and caustic potash in the 

 same way as normal pentane, and was fractionally distilled. 



Specific gravity at 074° . . . A = 0-67696 



. . . B = 0-67697 



Later determination with new specific- 

 gravity tube .... 0-67703 



Boiling-point under normal pressure . 68°-9o 



A second specimen was separated from American petroleum (petroleum 

 ether) by means of the combined dephlegmator and regulated temperature 

 still-head; but methyl pentamethylene, boiling at about 71-5°, is also present, 

 and cannot be removed by fractional distillation. Both this hydrocarbon 

 and isohexane are attacked much more readily than normal hexane by 

 fuming nitric acid ; and the eight fractions collected between about 66° and 

 69° were separately subjected to repeated and long-continued heating with 

 the acid. After this treatment seven of the fractions boiled constantly at 

 68-95°, and the specific gravities of the five lowest varied only between 

 0-67693 and 0-67702. 



3. Normal Heptane? — Dr. Tliorpe very kindly placed his well-known 

 specimen of normal heptane from Finns sahiniana at my disposal. 



Specific gravity at 0°/4°, .... 0-70048° 

 Boiling-point under normal pressure, . . 98-43° ^ 



4. Normal octane.^ — The specimen investigated was obtained from Kahl- 

 baum, and had been prepared from octyl iodide. The purification was in all 



1 Thomas and Young, Trans. Chem. See, Ixvii., p. 1071, 1895; Young, ijia?., Ixxiii., p. 905,1898. 



2 Trans. Chem. See, Ixxiii., p. 675, 1898. 



' Thorpe, Trans. Chem. See, xxxvii., p. 213, 1880. 

 * Trans. Chem. Soc, Ixxvii., p. 1145, 1900. 



SOIENT. PROG. H.D.S., VOL. XII., NO. XXXI. 3 G 



