A simple and quick test method was developed to distinguish thermally cracked materials, especially visbreaker residues and bitumens, from uncracked products, such as straight-run distillation bitumens and residues. The method is based on the reactivity of thermal residues and bitumens with phosphoric acid to form high-molecular-weight products that are clearly visible as black spots in a thin film of the treated material. © 1995.
De Filippis, P., Giavarini, C., Santarelli, M. L., & Scarsella, M. (1995). A simple test method for distinguishing straight-run from thermal (visbreaker) residues or bitumens. Fuel, 74(10), 1537–1539. https://doi.org/10.1016/0016-2361(95)00078-J