T-Stoff ([teː ʃtɔf]; 'substance T') was a stabilised high test peroxide used in Germany during World War II.
T-Stoff was specified to contain 80% (occasionally 85%) hydrogen peroxide (H2O2), remainder water, with traces (<0.1%) of stabilisers.
[5] Another of T-Stoff's many uses was to be combined as the oxidizer, with C-Stoff (methanol–hydrazine–water mixture) as the fuel, in the bipropellant Walter HWK 109-509 engine of the Messerschmitt Me 163 and Messerschmitt Me 263, at a ratio of approximately 3.1 parts T-Stoff oxidizer to one part C-Stoff fuel.
Because the two substances were so visually similar, a complex testing system was developed to make sure that each propellant was put into the correct tanks of the Messerschmitt Me 163.
This was because T-Stoff and C-Stoff are hypergolic propellants: they spontaneously ignite when mixed at normal temperatures.