The paper presents two large-scale observations of magnetic treatment of industrial water, aimed at investigating changes in the formation of deposits. First, a four-month experiment is described with two identical 25 kW heat exchangers, where in one case the inlet water was treated by a magneto-hydrodynamic method. Deposits recovered from both exchangers were analyzed chemically, by X-ray diffraction, infrared spectroscopy and PIXE. The amount of deposit for untreated water, composed mostly of calcite, increased exponentially with temperature reaching 20 g/m of tube at the warm end of the heat exchanger. The mass of the deposit for magnetically treated water did not depend on temperature and was only ca. 0.5 g/m of tube. It was composed of mainly noncrystalline silica-rich material. Further results were obtained from the practical installation at three blocks of a 1 GW power plant. The soft, amorphous deposit for magnetically treated water had a specific surface area of 80 m2/g and an infrared spectrum similar to that of a silicate hydrogel. Therefore, it appeared that, as a result of the passage through the magnetic device, crystallization of carbonates in water was blocked due to initiation of another, competitive process. This process is the activation of the colloidal silica, which will adsorb calcium, magnesium or other metal ions and then precipitate from the solution as the coagulated agglomerate. The most probable mechanism responsible for silica activation is a Lorentz-force induced deformation of the diffuse layer leading to the increased counterion concentration in the adsorption layer of the negatively charged silica.

Octacyanometallate-based compounds displaying a rich pallet of interesting physical and chemical properties, are key materials in the field of molecular magnetism. The [M(CN)₈]ⁿ⁻ complexes, (M = W^V, Mo^V, Nb^IV), are universal building blocks as they lead to various spatial structures, depending on the surrounding ligands and the choice of the metal ion. One of the functionalities of the octacyanometallate-based coordination polymers or clusters is the magnetocaloric effect (MCE), consisting in a change of the material temperature upon the application of a magnetic field. In this review, we focus on different approaches to MCE investigation. We present examples of magnetic entropy change ΔS_m and adiabatic temperature change ΔT_ad, determined using calorimetric measurements supplemented with the algebraic extrapolation of the data down to 0 K. At the field change of 5T, the compound built of high spin clusters Ni₉[W(CN)₈]₆ showed a maximum value of −ΔS_m equal to 18.38 J·K⁻¹ mol⁻¹ at 4.3 K, while the corresponding maximum ΔT_ad = 4.6 K was attained at 2.2 K. These values revealed that this molecular material may be treated as a possible candidate for cryogenic magnetic cooling. Values obtained for ferrimagnetic polymers at temperatures close to their magnetic ordering temperatures, T_c, were lower, i.e., −ΔS_m = 6.83 J·K⁻¹ mol⁻¹ (ΔT_ad = 1.42 K) and −ΔS_m = 4.9 J·K⁻¹ mol⁻¹ (ΔT_ad = 2 K) for {[Mn^II(pyrazole)₄]₂[Nb^IV(CN)₈]·4H₂O}_n and{[Fe^II(pyrazole)₄]₂[Nb^IV(CN)₈]·4H₂O}_n, respectively. MCE results have been obtained also for other -[Nb(CN)₈]-based manganese polymers, showing significant T_c dependence on pressure or the remarkable magnetic sponge behaviour. Using the data obtained for compounds with different T_c, due to dissimilar ligands or other phase of the material, the ΔS_m ~ T_c^−2/3 relation stemming from the molecular field theory was confirmed. The characteristic index n in the ΔS_m ~ ΔHⁿ dependence, and the critical exponents, related to n, were determined, pointing to the 3D Heisenberg model as the most adequate for the description of these particular compounds. At last, results of the rotating magnetocaloric effect (RMCE), which is a new technique efficient in the case of layered magnetic systems, are presented. Data have been obtained and discussed for single crystals of two 2D molecular magnets: ferrimagnetic {Mn^II(R-mpm)₂]₂[Nb^IV(CN)₈]}∙4H₂O (mpm = α-methyl-2-pyridinemethanol) and a strongly anisotropic (tetren)Cu₄[W(CN)₈]₄ bilayered magnet showing the topological Berezinskii-Kosterlitz-Thouless transition.

Successful incorporation of the Mn₁₂ molecules into silica channels has been attested with AC susceptometry and magnetocaloric effect measurements.

The experimental results of the susceptibility, specific heat, magnetization, and electron spin resonance of $\mathrm{Cu}{\left({\mathrm{H}}_2\mathrm{O}\right)}_2\left({\mathrm{C}}_2{\mathrm{H}}_8{\mathrm{N}}_2\right)\mathrm{S}{\mathrm{O}}_4$ are reported. Despite the triangular arrangement of chemical bonds, the system is identified as an $S=1∕2$ Heisenberg antiferromagnet where the dominant exchange coupling $J∕k_B\approx -1.4\mathrm{K}$ is mediated by a square network of hydrogen bonds. The long-range ordering observed at $T_N=0.91\mathrm{K}$ is proposed to be Néel type. The possibility of tuning the strength of the exchange couplings in various directions is discussed.