| | Contents | |
| | | Page |
| Table 16 | 1. Heat capacity of minerals | 228 |
| | 2. Heat capacity of rocks | 235 |
| | 3. Heats of transformation and of fusion | 237 |
| | 4. Heat capacity of gases | 241 |
| | Contents | |
| | | Page |
| Table 16 | 1. Heat capacity of minerals | 228 |
| | 2. Heat capacity of rocks | 235 |
| | 3. Heats of transformation and of fusion | 237 |
| | 4. Heat capacity of gases | 241 |
Heat capacities of minerals.—In the tables (in this section), the minerals are classified according to the first elements of their chemical formulae; for example, albite (NaAlSi8O8) will be found under sodium, and calcite (CaCO3) under calcium. The heat data are given in terms of absolute joules per gram (one joule = 0.23895 gram calories at 15°C.).
True or instantaneous heat capacities may be obtained by measuring the amount of heat needed to raise the temperature of the sample one degree or fraction thereof. This is the preferable type of data, available for many materials at low temperatures. At high temperatures this method is experimentally difficult because of large radiation losses so that ordinarily a different technique is employed—namely, the method of mixtures. (
See W. P. White, The Modern Calorimeter, N. Y., 1928.) This latter method yields data in the form of mean or interval heat capacities. The mean heat capacity is usually given for the temperature interval between 273.1°K. (0°C.) or room temperature and some higher temperature. The quantity measured is, however, the difference in heat content between some elevated temperature and that of the calorimeter. In order to convert these quantities to true heat capacities the mean heat capacity data (at constant pressure) are fitted to the equation
where
c̄p is the mean heat capacity at . . .
