## 2 Materials and Methods
### FTIR Spectroscopy  
In this paper, we also used the method of Fourier transform infrared spectroscopy (FTIR). The spectra were recorded using a spectrometer Nicolet 6700 (Thermo Fisher Scientific, Madison, WI, USA) in the transmittance mode in the wavenumber range of 6000-8000 cm\({}^{-1}\), i.e., in the near infrared (NIR) region. This region includes the absorption band of the first overtone of intramolecular stretching vibrations of water molecules.  
The overtone but not the main band was chosen due to the following reason. IR spectroscopy has been used to identify the differences in the average binding of water molecules between the analyzed solutions. The criterion of binding is the position of the absorption maximum of the NIR band which is directly related to the frequency of intramolecular vibrations of water molecules that depend on intermolecular binding. The shift of this band toward lower frequencies evidences an increase in the average energy of intermolecular hydrogen bonding, but normally the shift is very small, less than 1 cm\({}^{-1}\). The overtone band is more suitable for analyzing the shift, since its frequency is approximately doubled as compared to the main vibrational band, and it is shifted for a double distance along the wavenumber scale resulting in a two-fold increase in the sensitivity of the method.  
Each NIR spectrum was measured and averaged over 24 scans. The spectral resolution was 8 cm\({}^{-1}\), while zero-extension of the interferogram was introduced in such a way that the distance between the points in a spectrum was 1 cm\({}^{-1}\). A DTGS TEC detector with a KBr beam splitter was used. Prior to the Fourier transform, the Happ-Genzel apodization function was applied to the interferogram.  
During the measurements, the optical part of the IR spectrometer was purged with air with reduced content of water vapor and CO\({}_{2}\) using a dry air generator (Laboratory Gas Generator 74-5041). When recording the spectra, the temperature of the cuvette containing the sample was maintained at \(30\pm 0.5\)\({}^{\circ}\)C.  
The spectra of the studied solutions were recorded in a cuvette having various thickness with CaF\({}_{2}\) windows. Single-beam spectra were recorded successively at two different thicknesses of the sample: \(100\pm 1\)\(\upmu\)m and \(450\pm 1\)\(\upmu\)m. The spectrum of the sample in the thicker cuvette was divided by the spectrum of the sample in the thinner cuvette, allowing to obtain the transmittance spectrum of the analyzed solution with a thickness of \(350\pm 2\)\(\upmu\)m. Subsequently, a negative decimal logarithm was used to calculate the optical density spectrum from the transmittance spectrum. The spectra were smoothed using standard OMNIC software with averaging over 25 spectral points.  
Each of the powders studied was used to prepare 3 replicates of solution (10% w/w) for analysis in order to allow for experimental error. Infrared spectra were recorded 5 times for each of the solutions. Such number of observations is sufficient for evaluating the experimental error and comparing various solutions with special statistical methods described in the Section 2.6