After the birth of thermodynamics’ second principle—outlined in Carnot's Réflexions sur la puissance motrice du feu (1824)—several studies provided new arguments in the field. Mainly, they concerned the thermodynamics’ first principle—including energy conceptualisation—, the analytical aspects of the heat propagation, the statistical aspects of the mechanical theory of heat. In other words, the second half of nineteenth century was marked by an intense interdisciplinary research activity between physics and chemistry: new disciplines applied to the heat developed in the form of analytical, mechanical and statistical theories. Inside all these theories, entropy—the brand-new function that Clausius coined in his Mechanical theory of heat—started to play a central epistemic role. In the present paper, we analyse some steps of the historical process of conceptualisation of such function from 1850 to 1902. Particularly, we retrace the historical–foundational path that—starting from Clausius’ Second Law—lead Boltzmann and Gibbs to their distinguished formulations of statistical entropy. As usual, our research has been unrolled through the analyses of primary sources and by leaning on critical readings of the secondary literature. As for the methodological approach, text analysis of historical documents constituted our privileged modus operandi. This paper is the expression of a collaborative historical research program focused on the thermodynamic foundations of physics–chemistry relationship; early results have already been published by the same authors upon the concepts of reversibility––and––thermal equilibrium.

在卡诺的Réflexions sur la puissance motrice du feu (1824) 中概述的热力学第二原理诞生之后，一些研究在该领域提供了新的论据。他们主要涉及热力学的第一原理——包括能量概念化——、热传播的分析方面、热力学理论的统计方面。换句话说，十九世纪下半叶的特点是物理和化学之间激烈的跨学科研究活动：以分析、机械和统计理论的形式发展起来的应用于热的新学科。在所有这些理论中，熵——克劳修斯在他的热力学理论中创造的全新函数——开始发挥中心认知作用。在本文中，我们分析了从 1850 年到 1902 年这种函数概念化的历史过程的一些步骤。特别是，我们追溯了从克劳修斯第二定律开始的历史基础路径，导致玻尔兹曼和吉布斯对统计熵。像往常一样，我们的研究是通过对主要来源的分析和对二手文献的批判性阅读展开的。至于方法论，对历史文献的文本分析构成了我们的特权作案手法. 这篇论文是一个合作历史研究项目的表达，重点是物理-化学关系的热力学基础；同一作者已经发表了关于可逆性和热平衡概念的早期结果。