The absorption at three frequencies was investigated in particular, and the process clearly showed three stages. Experiments at three concentrations and in the temperature range of 4 • C to 9 • C suggested that both a higher initial concentration and elevated temperature above 6 • C were likely to result in a more erratic crystal growth. The faster the crystals grew through the field of view of the spectrometer, the higher was the change in absorption at all frequencies. The temperature effect on terahertz spectra was addressed as outlined previously [21], leading to the calculation of an equivalent liquid phase concentration. In addition, changes in the absorption coefficient were correlated with the composition and size of the hydration shell surrounding the salt ions.