the coloration with ferric chloride is red or bluish-violet Excess of
dilute alkali resolved all didepsides into their components at ordinary
temperatures. The didepsides of gallic, proto-catechuic, gentisinic, and
[Greek: b]-resorcylic acids precipitate gelatine and quinine acetate,
and in this respect approach the natural tannins.

The following summary gives an account of depsides which have been
prepared synthetically or which occur naturally:--[Footnote 1: _Ber._,
1908, 41, 2888; 1909, 42, 217; 1913, 45, 2718; 1913, 46, 1130, 2396,
1141, 1143; Liebig's _Ann._, 384, 230, 233, 238; 391, 356, 362.]

Di-_p_-hydroxybenzoic acid.
Di-_m_-hydroxybenzoic acid.
Disalicylic acid.
Diprotocatechuic acid.
Digentisinic acid.
Di-[Greek: b]-resorcylic acid.
_p_-Diorsellic acid.
_o_-Diorsellic acid.
_m_-Digallic acid.
Disyringic acid.
Di-_o_-cumaric acid.
Diferulic acid.
Di-[Greek: b]-hydroxynaphthoic acid.
_p_-Hydroxybenzoyl-_m_-hydroxybenzoic acid.
_m_-Hydroxybenzoyl-_p_-hydroxybenzoic acid.
Salicyl-_p_-hydroxybenzoic acid,
Vanilloyl-_p_-hydroxybenzoic acid.
Feruloyl-_p_-hydroxybenzoic acid.
[Greek: a]-Hydroxynaphthoyl-_p_-hydroxybenzoic acid.