244 RESEARCHES ON THE VOLATILE HYDROCARBONS 



ceased to have any action. The thermometer bulb extended into the liquid * nearly 

 to the bottom of the retort. A second thermometer was attached, by means of 

 flexible bands, to the side of the one in the retort ; the bulb being placed, during 



ebullition, at a point midway between the centre of the cork (— 5°) and the upper 

 end of the mercurial column, viz. at 35°. A paper screen, closely fitting the ther- 

 mometer spindle, was placed across at the top of the cork. With the retort neck 

 slightly inclined upward, and cooled to prevent the escape of vapor, ebullition was 

 continued for considerable time, until the mercury in the thermometer ceased to rise. 

 The lamp being removed for the moment, the neck of the retort was then turned 

 downward, and quickly inserted in a Liebig's condenser. On replacing the lamp, dis- 

 tillation commenced almost immediately at 79°. 



Observations 



Temperature. Time. Temper, by Side Thermom 



h. m. 



79.0 at 2.40 , R . . 



i 5 minutes. 

 79.2 « 2.45 , - „ 22°. 



\ 15 " 



79.4 " 3.00 12 „ 24°. 



79.5 " 3.12 20 „ 25°. 



79.6 " 3.32 lg a 26°. 

 79.6 " 3.50* 26°. 



common specific gravity bottle is not suited to this purpose. Indeed, with a volatile body that bottle cannot 



serve for an accurate determination at any temperature. A reform in this regard being highly 

 desirable, I would call attention to a specific gravity bottle which I obtained a few years ago 

 from Fastre, in Paris, which is admirably adapted for taking specific gravities, even of volatile 

 liquids, at a low temperature. The accompanying figure represents this bottle of one half its 

 natural size. "Who was the author of this particular form I am not informed, although it may 

 have been already noticed in some publication. A bottle analogous to this is figured by Schiel 

 (" Einleitung in das Studium der organischen Chemie," page 76) ; but his bottle has an oval 

 bottom, which makes it less convenient. The particular advantage of this bottle over the more 

 common one, which advantage Schiel omits to notice, consists in this : that the space or chamber 

 above the line on the capillary neck is large enough to allow for the expansion of the liquid 

 consequent upon the elevation of temperature from 0° to that of the surrounding air ; and that 

 the ground stopper fits so closely that no perceptible loss from evaporation can take place during 



the time occupied by an experiment. 



In order to furnish determinations of the specific gravities of the bodies to be treated of in these researches, 



which shall be comparable with corresponding determinations by other observers, I shall generally record one 



or more special determinations made for this purpose. 



* For critical remarks on the question of propriety of placing the thermometer bulb in the liquid, etc. ; and 



for further details of the method of taking boiling-points, especially at low temperatures, see the accompanying 



Memoir, " On the Influence of C 2 H 2 on the Boiling-points in Homologous Series of Hydrocarbons," etc 



