INTRODUCTION Almost all the procedures in the API Technical Data Book require pure component physical properties. This chapter provides a collection of properties for many hydrocarbons and selected non hydrocarbons. The compounds and the properties that were selected for inclusion in this chapter are those judged most useful for petroleum refining and associated industries. Further information on physical properties may be found in the Design Institute for Physical Properties Research (DIPPR) Data Compilation: Tables of Properties of Pure Compounds (8). The majority of data for the compounds in this chapter were taken from the following sources (in order of priority): 1. DIPPR Compilation (8) 2. GPA 2145-94 (13) 3. API Monograph Series (1-3) 4. TRC Tables (32-34@ 39-47) 5. Previous API Technical Date Book - Petroleum Refining (9). Unless otherwise indicated@ predictions of hydrocarbon data were made using the current Data Book procedures. Predictions of non hydrocarbon data were made using DIPPR Compilation (8) procedures. In addition to the pure component data tables (Sections IC1 through IC4)@ other general information is presented in this chapter. Section I A contains a list of constants and lists of conversion factors. Section 1B is a list of letter symbols with their definitions. Section 1C enumerates the property definitions with other pertinent information on the properties in the data tables. Note that the footnote codes in the data tables indicate whether data are predicted (P)@ extrapolated (T)@ experimental (no code)@ or if it is unknown whether the source is predicted or experimental@(S). Codes such as C@ G@ K@ and N provide further information for experimental data points. The key for these codes follows Table 1C4. Section IC5 is the reference key for the properties in the data tables. For the 1994 edition@ 14 hydrocarbons and five non hydrocarbons have been added to this chapter. The API identification numbers for the compounds that were in the previous edition have not been changed. However@ the added compounds were placed in the appropriate order on the physical property tables@ causing a departure from numeric order in the tables. This departure is considered necessary for maintaining consistency with the numbering used in other chapters. The data contained in Tables 1C1.1 through 1C4.12 are also available in computer readable format on tape or disk. The data are identical except that the number of significant digits may be different.