On the freezing process of sea water from data of laboratory measurements based on nuclear magnetic resonance

Abstract

Results of measurements of the relative brine content (Qm) and proton magnetic relaxation time (T1) in the liquid phase of freezing sea water at temperatures between −2°C and −43°C are given for variable directions of temperature changes using different pulse and stationary methods of NMR. The results are compared with current published evidence. The results of the temperature dependences of Qm at adding NaCl in sea water are shown. In all the cases, the hysteresis loops in the temperature dependencies of Qm and T1 in brine were discovered. They correspond to the crystallization range of the main salt of sea water (NaCl), which partially precipitates in the crystalline hydrate form (NaCl · 2H2O) at temperatures lower than −23°C. We demonstrate that crystalline hydrates begin to form in brine after complete salvatation of the ions of basic sea water salts at salinity from 85 to 90‰ and temperatures from −5 to −6°C. The determinations of Qm allowed us to calculate the salinity of brine, which agreed well with the current published estimates.