Na2CO32HNaCO32H2O

Trona Tro"na, n. [Of Egyptian or North African origin.] (Chem. & Min.) A native double salt, consisting of a combination of neutral and acid sodium carbonate, {Na2CO3.2HNaCO3.2H2O}, occurring as a white crystalline fibrous deposit from certain soda brine springs and lakes; -- called also {urao}, and by the ancients {nitrum}. [1913 Webster]