The second chapter addresses perhaps the most important topic of the book, i.e., the formulation. It is the formulation that will define the operating parameters for the process and can have a major impact on the design and construction of the dryer. Chapter 3 deals with the important role that water plays in the lyophilization process. The chapter not only shows the importance of purity but also describes properties such as supercooling and the electrical conductivity of ice. While it is true that the lyophilization process is designed to remove the water from the formulation, nevertheless, water will leave its mark on the cake structure.
Phase changes govern the lyophilization.
Chapter 4 was included to provide a review of the concepts of this topic and provide a foundation for succeeding chapters. While the shortest of all the chapters, its brevity does not diminish its importance. This chapter will serve as a reference source for discussions that occur in later chapters. An understanding of the principles set forth in Chapter 4 will prove useful in Chapter 5 that describes the thermal properties of a formation. It will be shown that some thermal properties such as the collapse or eutectic temperature, degree of supercooling and degree of crystallization are necessary to characterize the formulation while other properties like the formation of ice-like water clusters serve merely as a fingerprint for future reference.