## 3 Results
It needs to be emphasized that double magnesium and aluminum hydroxide hydrate easily form hydrotalcite-like compounds in the presence of carbon dioxide. However, there is no evidence of such a reaction on the XRD spectra, although the crystal structures of both phases are very similar [10; 23]. Based on the results of the thermal analysis, it can be observed that the course of changes in the case of samples with acids additions is almost the same, while for the reference sample it varies (Figure 3). For each sample, three main endothermic effects connected with the loss of mass of the samples can be observed. The first of those effects is placed around 186-202 \({}^{\circ}\)C and can be connected with the first step of decomposition of double magnesium and aluminum hydroxide and emission of interlayer water. These findings are confirmed on the EGA-MS curve (\(m/z=18\)), where the effect from water ions is observed. Moreover, the non-symmetrical character of this effect (longer arm for the lower range of temperatures) can indicate the amorphous character of double magnesium aluminum hydroxide hydrate or/and decomposition in this temperature range an additional phase, probably aluminum oxide hydrate [10; 24]. Figure 2: X-ray diffraction spectra of studied samples (1—reference sample; 2—sample with citric acid addition; and 3—sample with tartaric addition). At around 390 \({}^{\circ}\)C, another endothermic effect occurs, probably connected with the dihydroxylation of brucite and the second step of the decomposition of double magnesium and aluminum hydroxide hydrate. This effect is connected with the emission of CO2 with the maximum at ca. 413 \({}^{\circ}\)C (Figure 3b, EGA curve for \(m/z=44\)); this could be the evidence of the last stage of decomposition of hydrdalcite-like compounds. Despite the results of the XRD analysis, the short range of the temperature of this effect as well as the profile of the TG curve with a sharp loss of mass in this region do not fully support this claim, as some amount of poorly crystalline hydrdalcite-like phase maybe present in the samples [9,10,24,25]. At the temperature around 530 \({}^{\circ}\)C, the decomposition of boehmite follows [10]. Each of the above effects is connected with mass loss shown in Figure 4. During the first endothermal effects (up to 250 \({}^{\circ}\)C), the loss of mass of the samples was from around 0.81% mass for a sample without any additions, up to 1.82% for sample number 3 with an addition of tartaric acid. In the second effect, the loss of mass of the samples increases, also a sample with tartaric acid addition has the highest loss around 10.93% while the reference sample has only a loss of 10.35%. Taking into consideration that in the samples with an addition of chelates, MgO does not fully hydrate, it shows a strong influence of decomposition of double magnesium and aluminum hydroxide hydrate or/and hydrotalcite on a loss of mass in this range. Conversely, in the last identified effect, sample 1 has the highest loss of mass around 3.73% while the sample with tartaric acid has a loss of around 2.04%. The losses of mass and temperatures of the individual effects suggest that the qualitative phase composition is the same for each sample, and the depth of each effect is proportional to the content of the individual phases. This claim is supported by an XRD analysis. This is why, when taking into consideration the results of the thermal analysis, it can be stated that the addition of acids to the MgO-Al2O3-H2O system changes the phase composition in respect to its quantitative composition. The summary of the thermal effect with the loss of mass from the thermal analysis is shown in Table 3.  
Comparing the loss of mass in each effect, it can be noticed that in the two first effects, the loss is arranged in order from sample number 1, 2 and 3 at the end. In the case of the third effect, the order is the opposite.