recrystallised from acetic acid, forms small crystalline needles,
M.P. 273 -276 C., and yields fluorene on distillation with zinc dust.

----CO.O----
^ ---------- ^
| | | |
V ---O.CO--- V
OH

FLAVELLAGIC ACID, C_14H_6O_9, is obtained by the oxidation of gallic
acid with concentrated sulphuric acid and potassium persulphate. It
crystallises from pyridine in prismatic needles melting above 360
C. Distillation with zinc dust yields fluorene (see above)--

----CO.O----
^ ---------- ^ OH
| | | |
HO V ---O.CO--- V OH
OH OH

By heating ellagic acid for three-quarters of an hour at 185 C. with
concentrated sulphuric acid, ceruleo-ellagic acid (dioxyellagic acid),
C_14H_6O_10, is formed as yellowish needles, M.P. 360 C., which are but
little soluble in the usual solvents. The acid is slightly soluble in
strong caustic soda solution, the colour of the solution, on diluting,
changing to green and blue.

LUTEIC ACID (Luteo Saure, pentoxybiphenylmethylolide carboxylic
acid),C_14H_8O_9, occurs, in addition to ellagic acid, in myrabolams--
[Footnote: _Ber_., 1909, 42, 353.]