A simple approach for THE DETERMINATION AND CHARACTERI- ZATION OF TERNARY PHASE DIAGRAMS of aqueous two-phase systems composed of water, poly(ethylene) glycol and sodium carbonate EmanuEl V. CapEla, João H.p.m. SantoS, ISabEl boal-palHEIroS, pEdro J. CarValHo, João a.p. CoutInHo, SónIa p.m. VEntura, and mara G. FrEIrE University of Aveiro • Aveiro, Portugal Emanuel V. Capela is a Ph.D. student in Chemical Engineering at the University of Aveiro, Portugal. He received his Biochemistry M.S. degree in 2016 from the University of Aveiro, Portugal. His research interests cover the development of new platforms for the purifcation of biopharmaceuticals using ionic liquids. © Copyright ChE Division of ASEE 2019 112 ChE laboratory João H.P.M. Santos is a Ph.D. student in Chemical Engineering at the University of Aveiro, Portugal, in collaboration with São Paulo Universi- ty, Brazil. He received his M.S. degree in Industrial and Environmental Biotechnology from the University of Aveiro. His research interests are focused on PEGylation strategies for the production of therapeutic proteins. Isabel Boal-Palheiros is a lecturer in the Department of Chemistry, University of Aveiro, Portugal. She received her Ph.D. degree in 1997 in Inorganic Chemistry from the University of Aveiro, and she has taught mainly Physical Chemistry subjects. Her current research inter- ests comprise the properties and applications of ionic liquids. Pedro J. Carvalho is an Assistant Researcher at CICECO, Univer- sity of Aveiro, Portugal. He received his Ph.D. degree in Chemical Engineering from University of Aveiro in 2011, and from 2012 to 2016 he was a post-doctoral researcher at the same institution. His research focuses on the development of effcient recovery processes in petro- chemical refneries, and their modeling. João A.P. Coutinho is a Full Professor in the Chemistry Department of University of Aveiro, Portugal. He graduated in Chemical Engineer- ing from the University of Porto, Portugal, and received his Ph.D. in Chemical Engineering in 1995 by the Technical University of Denmark. He is active on the development of sustainable purifcation processes to be applied in biorefnery. Sónia P.M. Ventura is an Assistant Researcher at CICECO, University of Aveiro, Portugal. She received her Ph.D. degree in Chemical Engi- neering from the University of Aveiro in 2011, and was a post-doctoral fellow at the same institution from 2012 to 2014. She works on the Blue Biorefnery concept, developing alternative processes to recover bioactive compounds from marine biomass. Mara G. Freire is a Coordinator Researcher at CICECO, in the Chemistry Department of University of Aveiro, Portugal, and principal investigator of a European Research Council Grant. She received her Ph.D. degree in Chemical Engineering from the University of Aveiro in 2007. From 2008 to 2013 she was a post-doctoral researcher at ITQB2, New University of Lisbon, Portugal. Her main interests cover the development of sustainable and integrated purifcation strategies for biopharmaceuticals. A n important chapter of physical chemistry courses is based on the study of physical transitions that mixtures undergo upon temperature or composi- tion changes. Phase diagrams are an effcient tool to rep- resent this type of information, enabling one to grasp at a glance whether two or more substances are mutually misci- ble, or how pressure or temperature can be tuned to achieve a particular set of equilibrium conditions. The phase diagrams may be developed using the phase rule, which is, according to Peter Atkins, “the most elegant result of the whole chem- ical thermodynamics.” [1] However mathematically simple, the Gibbs’ formulation, i.e. the meaning and the defnition of phase and component, may not always be straightforward; for instance, when one or more species undergo a chemical reaction, the number of components may be diffcult to es- tablish. Also, the interpretation of phase diagrams, particu- larly the most complex ones, is not always easy to grasp by students. Beyond their conceptual pedagogical value, phase diagrams bear also a practical interest in the design of sepa- ration processes, with wide industrial use. Hence, phase di- agrams are an important subject to study and have a crucial role in the academic laboratories and in industry, in the felds of chemical engineering, chemistry and biotechnology. Aqueous Two-Phase Systems (ATPS) are ternary systems formed when two hydrophilic compounds are dissolved in water above certain concentrations, spontaneously separat- ing into two liquid phases. These systems were proposed by Albertsson [2] and can be formed by polymer/polymer, polymer/salt or salt/salt combinations, dissolved in aque- ous media. [3] ATPS have emerged as prominent purifcation platforms due to the water-richness of the phases, simplici- ty of preparation, high resolution capacity and ability to be scaled-up. [3] Among the different polymers, poly(ethylene) glycol (PEG) has been widely used in ATPS formulations Chemical Engineering Education