C4H6.(OH)4

Tetracid \Tet*rac"id\, a. [Tetra + acid.] (Chem.)
   Capable of neutralizing four molecules of a monobasic acid;
   having four hydrogen atoms capable of replacement ba acids or
   acid atoms; -- said of certain bases; thus, erythrine,
   {C4H6(OH)4}, is a tetracid alcohol.
   [1913 Webster]
    

Erythrite \E*ryth"rite\, n. [Gr. 'eryqro`s red.]
   1. (Chem.) A colorless crystalline substance, {C4H6.(OH)4},
      of a sweet, cooling taste, extracted from certain lichens,
      and obtained by the decomposition of erythrin; -- called
      also {erythrol}, {erythroglucin}, {erythromannite},
      {pseudorcin}, {cobalt bloom}, and under the name {phycite}
      obtained from the alga {Protococcus vulgaris}. It is a
      tetrabasic alcohol, corresponding to glycol and glycerin.