Set of Eiloart's solid formulae models with three stands.

These commercial models, first described by A. Eiloart, represent the three distinct forms of tartaric acid.

An asymmetric carbon atom (bound to four different groups) is imagined at the centre of each tetrahedron.

Models 1 and 2 represent the two optical active, d- and I- tartaric acids respectively and are mirror images.

Model 3 is optically inactive (mesotartaric acid). This is internally compensated since the two halves of the molecule produce opposite rotations.

A fourth form, also inactive, called racemic acid contains equal parts of the d- and I- forms and is externally compensated.