We present a part of the results obtained from a sounding rocket experiment devoted to the interplay between chemistry and interfacial-tension-driven hydrodynamic instabilities. The system studied was a combination of two immiscible liquids separated along an initially plane interface at which an interfacial reaction takes place. The reaction leads to an in-situ formation of a surface-active product. This system is studied in four integrated Hele-Shaw cells, developed in the project which were manually filled with onset of the microgravity phase. Basic diagnostic tools are two shadowgraph visualization systems of high resolution and two differential interferometer, each of them containing one cell. The experiment showed an intriguing dynamic interplay between cellular Marangoni convection and large-scale interfacial deformations. The focus of the presentation is on the discussion of the underlying mechanism of the latter.