In order to assess the accuracy and robustness of the predictions of the new methods, and also to train some of the machine learning submodels we employed, extensive quantum chemical and experimental datasets were constructed or compiled in this work. They are all collected in the SolProp data collection (), and an overview of the different databases is given in Table . More details on the databases in SolProp that are developed as part of this work are given in the supporting information (sections S.2, S.3, and S.5), while some important details are given below.