During this period, phase behavior became a central organizing principle in thermodynamics, with explicit pressure–temperature phase diagrams systematizing phase equilibria and melting curves across several substances. The kinetic theory was extended to viscosity and thermal conduction, unifying diffusion, heat transfer, and molecular motion within a single framework. Meanwhile, practical thermodynamics moved toward the rational design of heat transfer equipment, using correlations and data to connect theory with engineering practice and to quantify the role of oxygen in the energy released by organic compounds. Historical Significance: These advances laid the groundwork for modern thermodynamics of phase transitions and transport phenomena, with phase diagrams and quantitative transport data becoming indispensable tools in materials science and chemical engineering. The explicit connection between oxidation and heat of combustion refined calorimetry, energy budgeting, and the systematic compilation of thermodynamic data, shaping how later generations approached thermodynamics in both research and industry.