Regarding Physical and Chemical Transformations with the Involvement of Water Near -45 °C
Objective. A hypothesis about a new mechanism for accelerating chemical reactions involving supercooled water near -45 °С is presented. The hypothesis is based on the properties of the second critical point of water at a temperature of -53 °C and a pressure of 100 Mpa determined by computer modelling. Its influence extends to a special region of the phase space of cold water - the Widom line, which corresponds to -45 °С at atmospheric pressure. On the Widom line, an increase in entropy fluctuations and water density are predicted. It is assumed that an increase in the fluctuation of entropy leads to an increase in the fluctuation of the energy of water molecules and an acceleration of the chemical transformations. However, deep overcooling of bulk water is impossible due to its rapid crystallization below -37 °C. Methods. Deep cooling is possible if water is in nanoscale pores. The most convenient medium for this purpose is nanoporous silicate sorbents, in which a significant volume of pore water has parameters close to bulk metastable water. In an experiment using nanoporous moistened silicate sorbents, it is possible to achieve supercooling of water to -60 °С. In the performed experiment, thermometry of samples of silicate sorbents filled with hydrogen gas was performed. A chemical reaction was checked for near the Widom line. We also investigated the change in the physical properties of the medium using microwave spectroscopy. Results. In the experiment, it was possible to observe reactions of the interaction of hydrogen with the pore surface by the release of heat, as well as amplification of microwave radiation at a frequency of 34 GHz. Conclusion. Chemical reactions involving water, according to the proposed mechanism, can accelerate on the Widom line at temperatures from -45 °C to -53 °C and in the pressure range from 0 to 100 MPa.