Hierarchy classification:

1. top of the aat hierarchies
2. Materials Facet
3. Materials (hierarchy name)
4. materials (substances)
5. [materials by composition]
6. inorganic material
7. salt (inorganic material)

Anotations

Scope note:

A chemical compound; in conservation, a chelating agent of ammonium salt of citric acid used in solution for surface cleaning of paper, paintings, and other materials. May also be used as a buffering agent, preservative, and food additive.