C-Stoff ("C substance") was an reductant used in bipropellant rocket fuels developed by Helmuth Walter Werke in Germany during World War 2. It was developed for use with T-Stoff, concentrated hydrogen peroxide, which could also be ignited by a simple catalyst solution, Z-Stoff.
The proportions of the components in C-Stoff were developed to catalyse the decomposition of T-Stoff, promote combustion with the oxygen released by the decomposition, and sustain uniform combustion through sufficient quantity of the highly reactive hydrazine. The combination of the two fuels often resulted in spontaneous explosion, necessitating strict hygeine in fueling operations; there were numerous catastrophic explosions of the Messerschmitt Me 163 aircraft which employed this fuel system. Another hazard was toxicity to humans of each of the fuels.
