‎"DULONG, (PIERRE) & (ALEXIS) PETIT. - MEASURING QUANTITIES OF HEAT.‎
‎Untersuchungen über die gesetze der Ausdehnung fester, tropfbarer und elastisch-flüssiger Körper durch die Wärme, und über das wahre Maass der temperaturen.‎

‎(Leipzig, Barth), 1818. No wrappers. In: ""Annalen der Physik. Neue Folge. Herausgegeben von L.W. Gilbert"", Bd. 28, Drittes Stück. Pp. 233-344,(2) pp. a. 1 engraved plate. (Entire issue offered). The paper of Dulong & Petit: pp. 254-280.‎

Reference : 49062

‎First appearance in German (edited by Gilbert) of this, their (first) joint paper, which initiated the recheches leading to the the ""Law of Dulong and Petit"", the connection between atomic weight and atomic heat. The original Frensh having the title: Recherches sur les lois de dilation des solides, des liquides et des fluides élastiques, et sur la mesure exacte des temperatures.""""In 1815 Dulong’s famous collaboration with the mathematical physicist Alexis Thérèse Petit began"" it produced three important memoirs on heat (of which this is the first). The best-known part of this work is the statement of the law of constant atomic heats that bears their names, .... They began with the fundamental problem of measuring quantities of heat, which involved a critical analysis of thermometric scales. In 1804-1805 Gay-Lussac had carried out a comparison of mercury and air thermometers between 0°C. and 100°C. Dulong and Petit extended the range of comparison up to 300°C. and found an increasing discrepancy between the two scales at higher temperatures."" (DSB).‎