## 3 Results and Discussion  
The results of the IRT experiment carried out on the binary system of PA and SA are reported in Figures 4 and 5 and in Table 3.  
Figure 4: Phase diagrams comparison between the infrared thermometry method (IRT) experiment and literature data [15] for the palmitic acid (PA)–SA binary system. Figure 5: Comparison between the IRT experiment, differential scanning calorimetry (DSC) analysis and the numerical approach for the (PA–SA) binary system. The phase diagram plotted from the IRT experiments is compared to the experimental data collected from Reference [15] in Figure 4. The obtained diagram is consistent with the literature one [15]. The method succeeds in detecting the liquidus line, the eutectic, the peritectic, and even the metatectic transitions. On the right part of the phase diagram of the phase diagram, a transition is detected around 56.7 \({}^{\circ}\)C. This latter would most likely be a metatectic one given the overall shape of the phase diagram and considering results found in literature for other fatty acids' binary systems [15; 25; 26]. The presence of a metatectic transition implies the existence of a solid solubility domain. This domain is rather difficult to detect using the standard methods. In Reference [15], its location was estimated using Tamman plots but not backed by measurements performed using DSC or other methods. Moreover, the phase diagram presented in Figure 4 also shows other transitions on the left-hand side. Those transitions are coherent with the position of this potential solid solubility domain which would be a great advantage for the simple and fast IRT method in comparison with standard methods. The sample composition corresponding to the eutectic point is within the range of that found in the literature (see Table 3). Additionally, the droplet deposition on the aluminum plate and the numerical data treatment are not automated. It induces slight uncertainties during the sample preparation (size and composition) as well as during the data interpretation. Those user-induced uncertainties could explain some noticeable irregularities between adjacent points in the phase diagram (loss of continuity, missing data, eigenfunctions misinterpretation, etc.). Moreover, it appears that the temperature values related to the liquidus line are slightly underestimated with the IRT method. However, our DSC results are consistent with the IRT ones, as shown in Figure 5. Hence, this deviation could more likely be due to differences in pure components purities, inaccuracies in the samples' composition, and/or the user's interpretation of the thermograms. Despite these slight observed discrepancies between data, Figure 5 validates what is observed in Figure 4. The DSC thermograms for the sample with 86% PA-14% SA composition show that a phase transition occurs in the 57-58 \({}^{\circ}\)C range. However, a clear reading on the transition temperature could not be extracted and was therefore left aside to avoid including erroneous data. The IRT phase diagram coincides with the one obtained with the standard methods, suggesting that the IRT method is reliable to estimate the complex phase diagrams of fatty acids' binary systems. It provides the compositions and the temperatures at which several transitions occur (with the previously mentioned uncertainties). Moreover, this method allows the determination of approximately one hundred data sets in a single heating/cooling cycle (one hour to estimate this phase diagram), whereas the standard methods such as DSC or DTA require at least two to three cycles for a single composition (a few weeks to estimate this phase diagram). The results obtained using the IRT method are consistent with the DSC ones. Additionally, a solid-solid transition occurring around 50.5 \({}^{\circ}\)C was measured via DSC. This transition is consistent with IRT results, but it has not yet been found in enough samples to confirm the occurrence of such transition with certainty.