Planck's and Duhem's physical researches in the turning period between the 19th and 20th centuries

在这项研究中，我们已经表明，在马克斯·普朗克的物理研究过程中，有一个转折点，从可逆过程的热力学研究到不可逆过程的物理研究，大约在1890年。1890年，他研究了两种不同浓度电解溶液之间的电位差。在这种情况下，正离子和负离子由于浓度梯度而扩散（电扩散），因此以卡诺-克劳修斯原理为形式的热力学第二定律不能适用于这种情况。因此，普朗克详细地考虑了这一不可逆过程的基本物质机理及其定态，然后将流体力学方程和静电学（泊松方程）应用于此，推导出定态电位差公式。普朗克从1894年开始研究热辐射时，他认为热辐射是一种不可逆的现象，是通过线性电振子和电磁波相互作用进行的。他对这种情况的理论处理方法是对1890年研究不可逆电化学过程的方法的继承。在我们的研究中还说明，皮埃尔·迪昂在1900年初已经把他的研究从平衡热力学转向了不可逆热力学，他在后者研究中的结果是这一科学领域的初步成果。自1900年以来，普朗克成为原子论的热心支持者和推动者，而迪昂则对原子论和气体运动论持敌视态度。

In this study we have shown that in Max Planck's physical investigation processes there had been a turning point from the thermodynamic studies of reversible processes to the physical ones of irreversible processes around 1890. In 1890 he investigated the electric potential difference between two electrolytic solutions with different concentrations. In this case positive and negative ions diffuse due to concentration gradient (electrodiffusion) , so that the second law of thermodynamics in the form of Carnot-Clausius's principle can not be applied to this case. Planck, therefore, considered elementary material mechanism of this irreversible process and its stationary state in detail, then he applied hydrodynamic equations and electrostatics (Poisson's equation) to it, and derived a formula for electric potential difference in the stationary state. When Planck began to research thermal radiation since 1894, he regarded its phenomenon as an irreversible one, which progressed by mutual interactions between linear electric oscillators and electromagnetic waves. His method of theoretical treatment of this case was a succession of the former method in the investigation on irreversible electrochemical processes in 1890.Also in our research it has been explained that Pierre Duhem had shifted his investigations from equilibrium thermodynamics to irreversible thermodynamics in the beginning of 1900, and his results in the latter investigations were the initial fruits in this scientific field. Since 1900 Planck became an ardent supporter and promoter of the atomistic theory, on the other hand, Duhem kept a hostile attitude against the atomism and the kinetic theory of gases.