286 On the Elastic Force of the Vapor of Mercury. 



Art. X. — Memoir on the elastic force of the vapor of Mercury, at 

 different temperatures ; by M. Avogadro.''^ 



Translated for this Journal, by Prof. A. D. BACHE.t 



The experiments of Dniong and Petit, give for the boiling point 

 of mercury, under the atmospheric pressure, 680° F.J estimated by 

 the mercurial thermometer, and 662° F.§ by the air thermometer, 

 corrected for the expansion of glass.' At this temperature, then, the 

 maximum tension of mercurial vapor corresponds to a pressure of 

 about thirty inches of mercury. I am not aware that any experi- 

 ments have been made to ascertain the tension of this vapor at tem- 

 peratures either below or above its boiling point. Such a research 

 cannot fail to be interesting, whether we consider its results as mere 

 additions to the list of properties of this valuable metal, or in their con- 

 nexion with the facts, already developed, in relation to the vapors 

 of other liquids. In this latter point of view, it may serve to lest the 

 truth of existing opinions, in relation to the laws of vaporization. 



The object of the memoir, of which this paper is an extract, is to 

 give the result of certain experiments, made with the views just sta- 

 ted, and their application to test the formulae by which the tensions of 

 the vapors of other liquids, in terms of the temperature, have been 

 represented. 



My experiments were made at temperatures below the boiling 

 point of mercury : near enough, however, to that point, and extend- 

 ing through a sufficient range of temperature, to determine the law 

 of tension with some precision. In order to have applied the meth- 

 od by which Dalton determined the tension of the vapor of water 

 between 32° and 212° F., namely, the depression of the column of 

 mercury in a barometer tube by the tension of the vapor, I must have 

 heated the upper part of the tube, uniformly, and to a temperature 

 between 390° and 570° F.,|| by surrounding it with a liquid 



* Extract communicated by the author to the Editors of the Annales de Chimie 

 et de Physique. The entire Memoir is contained in the thirty-sixth volume of the 

 Memoirs of the Academy of Turin. 



t In the original memoir, the degrees of the Centigrade scale are referred to, both 

 in the observations and in the formula. I have supposed that the translation would 

 be rendered more acceptable, by converting the degrees of the Centigrade ther- 

 mometer into those of Fahrenheit's scale, and by adapting the formulae to the same 

 scale. The original temperatures and formula will be given at the bottom of the 

 page on which they may occur. — [Translator.'] 



tSeOOC. §350°C. II 200° to 300OC. 



1 



