Some appear to be glucosides of gallic acid, since they yield this acid and a sugar on hydrolysis, e.g.
The solvating waters actively participate in the hydrolysis mechanism.
The first term includes simple sugars containing two to nine atoms of carbon, which are known severally as bioses, trioses, tetroses, pentoses, hexoses, &c.; whilst those of the second group have the formula C12H22011 and are characterized by yielding two monosaccharose molecules on hydrolysis.
When sodio-malonic ester is condensed with trimethylene bromide the chief product is ethyl pentane tetracarboxylate, tetramethylene dicarboxylic ester being also formed, and from this the free acid may be obtained on hydrolysis.
The changes conditioning rancidity, although not yet fully understood in all details, must be ascribed in the first instance to slow hydrolysis ("saponification") of the oils and fats by the moisture of the air, especially if favoured by insolation, when water is taken up by the oils and fats, and free fatty acids are formed.
