Diagram, 'Spectrum of spinel (magnesium aluminate)' by William Crookes A diagram in pencil, labelled figure 2, showing a spectrum for magnesium aluminate. Includes a note to the engraver. Subject: Chemistry / Spectroscopy A print of this diagram was published in volume 42 of the Proceedings of the Royal Society alongside the paper 'On the crimson line of phosphorescent alumina'. 1886