1818.] If. Gay-Lussac on the Boiling Point of Fluids. 129 



Article XIV. 



Notice respecting the Fixedness of the Boiling Point of Fluids. 



By M. Gay-Lussac* 



In the memoirs of the Academy of Berlin for the year 1785, 

 p. 2, or in the Annales de Chimie, x. 49, we have a set of expe- ■ 

 riments by M. Achard, the object of which was to ascertain 

 whether the degree of heat of pure boiling water be fixed and 

 invariable, independent of the pressure of the atmosphere. He 

 deduced two conclusions from his experiments: 1. That, in a 

 metallic vessel, water has not a fixed point of ebullition, but that, 

 while it continues boiling, its temperature is constantly varying, 

 and that this variation is principally produced by the action of 

 the air, both upon the sides of the vessel and upon the surface: 

 of the water, while, in a glass vessel, boiling water has a fixed 

 and determinate degree of heat, without the action of the external 

 air upon the sides of the vessel producing any change in the 

 state of the fluid. 2. That the nature of the vessel has no 

 influence upon the degree of heat which the water acquires in 

 boiling. There is, however, reason to suppose that M. Achard's 

 experiments are not correct, and that they were so made that 

 the results cannot be accurately compared together. 



M. Gay-Lussac, some years ago, observed that a thermometer, 

 which marked exactly 212 Fahr. (100 cent.) in water boiling in a 

 vessel of tinned iron, did not stop at the same degree in a vessel 

 of glass, although the circumstances appeared in other respects 

 quite similar. The difference was about two degrees Fahr. and as 

 there seemed no way of accounting for it but the nature of the 

 vessel, he concluded that water boils sooner in a metallic than 

 in a glass vessel/f - 



Prof. Munche, of Heidelberg, in conjunction with M. Gmelin, 

 has made a number of experiments in vessels of different kinds, 

 and nearly of the same form, the results of which he conceives 

 are unfavourable to M. Gay-Lussac's position. Upon examining 

 into the nature of M. Munche's experiments, M. Gay-Lussac does 

 not, however, conceive that they afford any real objection to his 

 former opinion ; many of the results in fact coincide with it, and 

 with respect to the rest, they do not appear sufficiently satis- 

 factory to entitle us to form any general conclusion contrary 

 to it. 



With respect to the cause of the difference, M. Gay-Lussac 

 conjectures that it may depend both upon the conducting power 

 of the substance of the vessels and upon the polish of the 

 surfaces. In illustration of the subject he states the following 



• Abridged from the Ann. de Chim. ft de Pliys. vii. 307. (March, 181K. > 

 + Ann.de Cliim. lxxxii. 174. 



Vol. XII. N° II. I 



