pyrosulfuric acid
noun
py·ro·sulfuric acid
"+…-
: an unstable, crystalline acid H2S2O7 that is usually handled commercially as a thick oily fuming liquid, that is formed by the union of sulfur trioxide with sulfuric acid, that is a chief component of fuming sulfuric acid, and that is converted to sulfuric acid when mixed with water
called also disulfuric acid
compare oleum
Word History
Etymology
International Scientific Vocabulary pyr- + sulfuric