Sunburns may be avoided by the liberal use of a sunscreen containing either an opaque active ingredient such as zinc oxide or titanium dioxide or a nonopaque active ingredient such as PABA (para-aminobenzoic acid) or benzophenone.
On fusion with caustic potash it decomposes with formation of tetrahydroxy-benzophenone, which then breaks up into resorcin and hydroquinone.
Benzophenone oxime, CeHSC (:NOH)C 6 H 5, exists only in one modification which melts at 140° C.; whereas the unsymmetrical benzophenones each yield two oximes.
Distillation of its calcium salt gives benzophenone with small quantities of other substances, but if the calcium salt be mixed with calcium formate and the mixture distilled, benzaldehyde is produced.
BENZOPHENONE (DIPHENYL KETONE), C 6 H 5 CO.
Many derivatives are known, thus ortho-amino-benzophenone, melting at 106° C., can be obtained by reduction of the corresponding nitro compound; it condenses under the influence of heated lead monoxide to an acridine derivative and with acetone in presence of caustic soda it gives a quinoline.
Tetramethyl-diamido-benzophenone or Michler's ketone, CO[C6H4N (CH3)2]2, melting at 173°, is of technical importance, as by condensation with various substances it can be made to yield dye-stuffs.
Diphenylfulven, from benzophenone and cyclo-pentadiene, crystallizes in deep red prisms. Dimethylfulven is an orangecoloured oil which oxidizes rapidly on exposure.