If a suitable prism is placed in front of the eyes the double vision may be prevented.
Ladenburg's prism formula would give two enantiomorphic ortho-di-substitution derivatives; while forms in which the hydrogen atoms are placed at the corners of a regular octahedron would yield enantiomorphic tri-substitution derivatives.
- are cut off from the end of the prism turned towards the body o the stem.
By projecting Ladenburg's prism on a plane and numbering the atoms so as to correspond with Kekule's form, viz.
When the pupil of the eye is held half over the edge of the prism a, one sees the image of the object with one half of the pupil and the paper with the other half.