Table 6. Characteristic Points in DSC Curves and Optically Determined Freezing Point of Narrow Boiling Range Distillation Cuts of Synthetic Distillatea.
| initial boiling point (°C) | DSC onset of freezing (°C)b | DSC end of melting endotherm (°C)b | freezing point, optical determination (°C)c | enthalpy of phase change during freezing (J g–1) | enthalpy of phase change during melting (J g–1) |
|---|---|---|---|---|---|
| 195 | d | –62.2 | e | c | 9 |
| 200 | –66.1 | –56.0 | –57 | –7 | 11 |
| 205 | –60.4 | –47.5 | –48 | –10 | 11 |
| 210 | –58.1 | –43.2 | –43 | –9 | 13 |
| 215 | –57.5 | –41.3 | –41 | –15 | 15 |
| 220 | –57.0 | –41.0 | –41 | –14 | 15 |
| 225 | –55.6 | –46.5 | –47 | –19 | 20 |
| 230 | –53.7 | –42.7 | –43 | –17 | 19 |
| 235 | –50.8 | –39.1 | –41 | –16 | 19 |
| 240 | –47.7 | –37.2 | –37 | –17 | 19 |
| 245 | –47.5 | –30.8 | –30 | –21 | 22 |
| 250 | –42.7 | –25.6 | –25 | –20 | 21 |
| 255 | –41.7 | –25.4 | –25 | –18 | 20 |
| 260 | –40.7 | –31.2 | –31 | 19 | 21 |
| 265 | –35.7 | –26.6 | –27 | –16 | 21 |
| 270 | –34.1 | –24.6 | –25 | –17 | 21 |
| 275 | –33.2 | –23.8 | –23 | –22 | 22 |
| 280 | –31.2 | –21.0 | –20 | –23 | 23 |
| 285 | –29.3 | –18.6 | –18 | –24 | 24 |
| 290 | –26.9 | –17.7 | –17 | –24 | 26 |
| 295 | –25.7 | –15.4 | –15 | –23 | 23 |
| 300 | –22.8 | –14.8 | –15 | –24 | 23 |
| 305 | –21.9 | –11.6 | –11 | –24 | 25 |
| 310 | –16.3 | –10.3 | –10 | –23 | 25 |
| 315 | –16.4 | –7.9 | –7 | –24 | 25 |
| 320 | –11.9 | –3.9 | –4 | –27 | 25 |
a
The final boiling point is 5 °C above the initial boiling point; for samples with boiling point below 195 °C, freezing was not induced.
c
Optical determination of wax crystal dissolution (see the Section 2). Reproducibility of the method is ±1.3 °C according to the instrument manufacturer; therefore, the first decimal is omitted.
d
Freezing induced during hold time at −70 °C.
e
Cooling insufficient to induce freezing.