Volume I presents a simplified technique for the practical application of thermodynamics by students, engineers, materials scientists, geologists, chemists, & others concerned with metals/materials related problems. This technique incorporates Kirchoff's Law as a four step procedure structured around a thermodynamic loop or "TL" similar to that used to describe engine performance in materials systems. The TL approach affords the reader a framework for using a vast store of tabulated & graphical data, including phase diagrams. This text places an emphasis on solving practical problems rather than generating new data. Volume II provides solutions to the example problems presented in Volume I & introduces the reader to problems of a wider scope that extend to the application of the thermodynamic loop.