zinc-alumhttp://www.oed.com/dictionary/zinc-alum_n%3Ftab%3Dmeaning_and_usezinc-alum, n.
First published 1921; not fully revised

zinc-alumnoun

  1. 1851–
    (See quots.).
    1. 1851
      Sulphate of Alumina and Zinc-oxide.—Zinc-alum = ZnO,SO3 + Al2O3,3SO3 + 24Aq.
      H. Watts, translation of L. Gmelin, Hand-book of Chemistry vol. V. 46

Originally published as part of the entry for zinc, n.

zinc, n. was first published in 1921; not fully revised.