Nitrile rubber-resin mixtures were found to be good sealants for precision instrument cabins as well as large engine cases owing to their excellent adhesion to metals，good water-tight and air-tight properties，and appropriate resistance to heat and ageing．During preparation of such mixtures，the author noticed that in the presence of metallic oxides，sulphur and T.M.T.D.，the solution mixture gelatinized gradually at room temperature while the free sulphur content gradually decreased．The vulcanizing effects were further proved by the solvent extraction test of the gelatinized mass，although the crosslinking was found to be far much less than those caused by vulcanizing at higher temperatures．