Editing Citric acid (section)

===Cleaning and chelating agent===
[[File:Fe2CITdianion.svg|thumb|144px|left|Structure of an iron(III) citrate complex<ref name="xiang">Xiang Hao, Yongge Wei, Shiwei Zhang (2001): "Synthesis, crystal structure and magnetic property of a binuclear iron(III) citrate complex". ''Transition Metal Chemistry'', volume 26, issue 4, pages 384–387. {{doi|10.1023/A:1011055306645}}</ref><ref name="shweky">{{cite journal|doi=10.1021/ic00101a001|title=Syntheses, Structures, and Magnetic Properties of Two Dinuclear Iron(III) Citrate Complexes|year=1994|last1=Shweky|first1=Itzhak|last2=Bino|first2=Avi|last3=Goldberg|first3=David P.|last4=Lippard|first4=Stephen J.|journal=Inorganic Chemistry|volume=33|issue=23|pages=5161–5162}}</ref>]]
Citric acid is an excellent [[chelation|chelating agent]], binding metals by making them soluble. It is used to remove and discourage the buildup of [[limescale]] from boilers and evaporators.<ref name="ullmann" /> It can be used to treat water, which makes it useful in improving the effectiveness of soaps and laundry detergents. By chelating the metals in [[hard water]], it lets these cleaners produce foam and work better without need for water softening. Citric acid is the active ingredient in some bathroom and kitchen cleaning solutions. A solution with a six percent concentration of citric acid will remove hard water stains from glass without scrubbing. Citric acid can be used in shampoo to wash out wax and coloring from the hair. Illustrative of its chelating abilities, citric acid was the first successful [[eluant]] used for total ion-exchange separation of the [[lanthanide]]s, during the [[Manhattan Project]] in the 1940s.<ref>{{Cite journal|last1=JOHNSON|first1=WARREN C.|last2=QUILL|first2=LAURENCE L.|last3=DANIELS|first3=FARRINGTON|date=1947-09-01|title=Rare Earths Separation Developed on Manhattan Project|url=http://dx.doi.org/10.1021/cen-v025n035.p2494|journal=Chemical & Engineering News Archive|volume=25|issue=35|pages=2494|doi=10.1021/cen-v025n035.p2494|issn=0009-2347}}</ref> In the 1950s, it was replaced by the far more efficient<ref>{{Cite journal|date=2020-08-01|title=Individual and combined application of EDTA and citric acid assisted phytoextraction of copper using jute (Corchorus capsularis L.) seedlings|url=https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=Individual+and+combined+application+of+EDTA+and+citric+acid+assisted+phytoextraction+of+copper+using+jute+%28Corchorus+capsularis+L.%29+seedlings&btnG= |journal=Environmental Technology & Innovation|volume=19|pages=100895|doi=10.1016/j.eti.2020.100895|issn=2352-1864|last1=Saleem|first1=Muhammad Hamzah|last2=Ali|first2=Shafaqat|last3=Rehman|first3=Muzammal|last4=Rizwan|first4=Muhammad|last5=Kamran|first5=Muhammad|last6=Mohamed|first6=Ibrahim A.A.|last7=Khan|first7=Zaid|last8=Bamagoos|first8=Atif A.|last9=Alharby|first9=Hesham F.|last10=Hakeem|first10=Khalid Rehman|last11=Liu|first11=Lijun|bibcode=2020EnvTI..1900895S |s2cid=219432688}}</ref> [[Ethylenediaminetetraacetic acid|EDTA]].

In industry, it is used to dissolve rust from steel, and to [[Passivation (chemistry)|passivate]] [[stainless steel]]s.<ref>{{Cite web|url=https://www.astm.org/Standards/A967.htm|title=ASTM A967 / A967M - 17 Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts|website=www.astm.org}}</ref>