Over the years, ionic liquids have received increased attention in several fields of application. More specifically a new ionic liquid family was developed, called protic ionic liquids, that have been proven to be biodegradable and they have potentially low toxicity, besides their low cost of preparation, simple synthesis and purification are interesting features. Continuing with our systematic work on synthesis and characterization of protic ionic liquids, this work deals with the synthesis, FT-infrared identification and thermodynamic characterization of two new ionic liquids, 2-hydroxyethylammonium stearate, (2-HEAS) and bis(2-hydroxyethylammonium) stearate (B2HEAS), based in the neutralization reaction of stearic acid with 2-hydroxyethylamine and bis(2-hydroxyethylamine) (generally known as mono and diethanolamine, respectively). Thermal properties of ionic liquids in function of temperature and concentration, along with the volumetric properties were determined. Results showed that both ionic liquids (2-HEAS and B2HEAS) form micelles, suggesting interfacial activity. Also, low negative deviations from ideality for the two binary systems were observed. (C) 2014 Elsevier B.V. All rights reserved.