## 3 Discussion
The authors interpreted the shift of the absorption maximum of water in the near-IR spectrum for water in a magnetic field with an induction of 14 T as an increase in hydrogen bonds [41]. In another study, the authors attributed the decrease in surface tension and increase in water viscosity when exposed to a 500 mT magnetic field to the increasing the number of hydrogen bonds [42]. On the other hand, there are works that show, on the contrary, a decrease in hydrogen bonds in strong magnetic fields. A large number of hydrogen bond breaks under the influence of a magnetic field with an induction of 200 mT or more was recorded in [43]. Effects of a decrease in the friction coefficient were found in [44] and a decrease in heat capacity and boiling point in [45] can also be interpreted as a decrease in the quantity of hydrogen bonds. Changes in the number of hydrogen bonds in water can explain the increase in the yield of peroxide with an increase in the magnetic field induction in our experiments. However, the effect of increasing peroxide is associated with a decrease in molecular oxygen in the water. It is characteristic that both of these effects depended on the concentration of NaCl, while the changes in pH and redox potential did not. It is interesting that previous authors had also recorded the dependence of magnetic effects on the concentration of solutes. For example, from NH4 Cl in [46] or d-glucose [41]. When studying the effect of a magnetic field on the concentration of molecular oxygen dissolved in deionized water and in aqueous NaCl solutions, a decrease in the concentration of dissolved molecular oxygen with an increase in the magnetic field induction was shown (Figure 5). The magnitude of this effect depends on the concentration of NaCl. It transpired that an increase in the redox potential cannot be explained by a decrease in the molecular oxygen concentration. We assume that this change is associated with the generation of reactive oxygen species. Indeed, when a magnetic field acts on aqueous solutions, hydrogen peroxide is produced, which depends on field induction (Figure 6). The relative increase in hydrogen peroxide generated is higher as NaCl concentration increases. A possible mechanism for the generation of peroxide in an aqueous solution is the reduction of singlet oxygen to a superoxide anion radical, the protonated form of which dismutes to form hydrogen peroxide and a singlet oxygen molecule [47; 48; 49]. However, another mechanism of relatively rapid changes of concentration of molecular oxygen under magnetic field exposure is possible. It is known that nano-bubbles can exist in water for a long time [50]. A decrease in the concentration of molecular oxygen may also indicate the transfer of oxygen dissolved in the water into these bubbles. To obtain stable results during experiments, it was often necessary to stir the solutions. On the one hand, it has already been shown that mixing can affect the basic physicochemical properties of water and, consequently, aqueous solutions [38]. In the present study, it was found that flow-mixing of solutions using a microfluidic system does not affect the measurement of pH and the concentration of molecular oxygen. However, it can change the redox potential of NaCl solutions under certain conditions. This may mean that redox reactions in salt solutions prepared using solutions (NaCl or water) diluted by flow-mixing will proceed differently than in similar salt solutions prepared with unmixed water. One noteworthy point is that measurements were carried out immediately after exposure to the magnetic field. It would certainly be better to carry out measurements directly during exposure and we plan to perform such experiments. However, the experiment plan in its present form makes sense as there is evidence that the effects of strong magnetic fields on aqueous solutions persist for minutes or even tens of minutes.