Alum

1. Any hydrous, alkali aluminum sulfate mineral, including kalinite, potassium alum, sodium alum, mendozite, tschermigite, and lonecreekite. Syn: potash alum
2. A former name for kalinite and potassium alum.
3. Any salts that are double sulfates of aluminum, chromium, iron, or manganese and one of the alkali metals.
   Source: Dictionary of Mining, Mineral, and Related Terms

A type of immune adjuvant (a substance used to help boost the immune response to a vaccine). Also called aluminum sulfate.