We propose low-resolution scans of a selected sample of symbiotic binaries in order to investigate physical processes generating the IR emission of these objects. Our principal aim is to study the properties of dust formed in symbiotic binaries. Symbiotics provide a different physical environment for dust formation and dust emission than single red giants. The hot (T = 80000K - 150000K) companion affects the wind properties of the red giant, and very likely also the dust formation and dust emission. Differences of IRAS colours between single red giants and symbiotic systems containing red giants of the same spectral type indicate that the physical conditions in the dust shell are indeed dramatically influenced by the hot companion in the binary. We expect from our proposed ISO observations to allow a decisive advance in the understanding of symbiotic systems. Low resolution spectroscopy in the 2.4-197 um range will most probably answer the puzzling question, why the symbiotic phenomenon arises only in three different, well defined situations with regard to the cool giant's classification and the symbiotic subclass. For example, we hope to find the solution why there is no symbiotic system with an orbit typical for D-types, but containing a non-Mira type giant. In addition, we believe that dust formation theories will profit as well from the unique physical conditions encountered in symbiotic binaries.