This meant that about 75 times the propellant would immediately ignite when exposed to flash, as compared to the U.S. powder. British ships had inadequate protection against these flash fires. German propellant ("RP C/12", handled in brass cartridge cases) was less vulnerable and less volatile in composition. German propellants were not that different in composition from cordite—with one major exception: centralite. This was symmetrical diethyl diphenyl urea, which served as a stabiliser that was superior to the petroleum jelly used in British practice. It stored better and burned but did not explode. Stored and used in brass cases, it proved much less sensitive to flash. RP C/12 was composed of 64.13% nitrocellulose, 29.77% nitroglycerine, 5.75% centralite, 0.25% magnesium oxide and 0.10% graphite.