Aluminum sodium sulfate

E number E521CAS 10102-71-3

Listed as an acidity regulator, a raising agent and a firming agent by Canada and the US.

Listed as acidity regulators (CA, US) · raising agents (CA, US) · firming agents (CA, US)
Chemical structure of Aluminum sodium sulfate, from PubChem compound 24939
Structure from PubChem CID 24939 (National Library of Medicine, public domain). A depiction of one compound: where a listing covers a family, or a substance has no single structure, this page shows none.

Aluminium sodium sulfate is a firming agent and a raising-agent component in some baking powders.

Where it is and isn’t permitted

Status of Aluminum sodium sulfate by jurisdiction. Every jurisdiction this site covers is listed, including those where the substance does not appear.
JurisdictionStatusScope and limitsCitation
Australia and New ZealandFood Standards Australia New ZealandNo listed food uses foundThis site has not matched this substance to any food use on this jurisdiction’s list of authorised food additives. A food additive may be used only in foods that list names. Flavourings, enzymes, processing aids and added nutrients are regulated separately and do not appear on it.
CanadaHealth CanadaPermitted, with conditions

highest permitted level 2,200 mg/kg

5 permitted uses

Show every permitted use
  • In: Pickles and relishes. Purpose: Firming agent. Limit: 15 ppm. Amendment notices: M-FAA-25-03. — Health Canada, List of Permitted Firming Agents (List 6), item S.1
  • In: White flour; Whole wheat flour. Purpose: Carrier of benzoyl peroxide. Limit: If used singly, the amount not to exceed 900 ppm. If used in any combination with other carriers of benzoyl peroxide, set out in this list or in sections 12.1.1 and 12.1.3 of Volume 12 of the Food Compositional Standards Document, the total combined amount not to exceed 900 ppm. — Health Canada, List of Permitted Food Additives with Other Purposes of Use (List 8), item S.5
  • In: Baking powder. Purpose: Acid-reacting material. Limit: 4%, calculated as aluminum. Amendment notices: M-FAA-25-03. — Health Canada, List of Permitted Acidity Regulators and Acid-Reacting Materials (List 10), item S.5(a)
  • In: Batter; Breading; Dry batter coating mixes. Purpose: Acid-reacting material. Limit: 2,200 ppm, calculated as aluminum. Amendment notices: M-FAA-25-03. — Health Canada, List of Permitted Acidity Regulators and Acid-Reacting Materials (List 10), item S.5(b)
  • In: Unstandardized bakery products. Purpose: Acid-reacting material; Acidity regulator. Limit: 2,200 ppm, calculated as aluminum. Amendment notices: M-FAA-25-03. — Health Canada, List of Permitted Acidity Regulators and Acid-Reacting Materials (List 10), item S.5(c)
Health Canadaand 4 further provisionsretrieved 2026-10-17
European UnionEuropean Commission / EFSAPermitted, with conditions

1 food category

Permitted as a member of Aluminium sulphates. Note 1: The additives may be added individually or in combination.

Regulation (EC) No 1333/2008, Annex II, as amended by (EU) No 380/2012, via Aluminium sulphatesretrieved 2026-10-18
Great BritainFood Standards Agency / Food Standards ScotlandPermitted, with conditions

1 food category

highest permitted level 200 mg/kg or mg/l

Permitted as a member of E 520–523: Aluminium sulphates. ML = 200. only candied cherries Period of application: from 1 February 2014. Note (1): The additives may be added individually or in combination. Note (38): Expressed as aluminium.

Assimilated Regulation (EC) No 1333/2008, Annex II (as at 28 June 2024), via E 520–523: Aluminium sulphatesretrieved 2026-10-18
JapanConsumer Affairs AgencyNo listing matchedThis site imports only Japan’s list of designated additives (Appended Table 1 to the Regulations for Enforcement of the Food Sanitation Act), matched by English name. Existing additives, natural flavouring agents and ordinary foods used as additives are permitted outside that list and are not imported, so an empty row does not show that Japan does not permit the substance.
South KoreaMinistry of Food and Drug SafetyNo listing matchedThis site imports Part III of South Korea’s Standards and Specifications for Food Additives, matched by CAS number, then INS number, then exact name. Mixed preparations and sanitisers are not imported, and an entry whose identifiers disagreed with a page’s is held for review, so an empty row does not show that South Korea does not permit the substance.
United StatesFood and Drug AdministrationPermitted21 CFR 182.1131retrieved 2026-10-17
Codex AlimentariusCodex Alimentarius Commission / JECFANot listedDoes not appear on this jurisdiction’s permitted list. That is not the same as being prohibited.

How much is permitted

A listing usually limits the quantity as well as the food. Only one of the forms that takes is a figure: quantum satis and good manufacturing practice permit the amount the technological effect requires and no more, which is a limit rather than the absence of one. Figures below are the range across every food category this page is listed in, and categories differ between regulators — see how much is permitted.

Canada15 mg/kg – 40,000 mg/kg4 numeric limit, 1 no quantity stated
European Union—1 no quantity stated
Great Britain200 mg/kg1 numeric limit
United States—1 no quantity stated

What it is made from

Crystallised from aluminium sulfate and sodium sulfate together.

  • Vegan
  • Vegetarian

Compare other additives on the dietary indexes.

CAS registry number
10102-71-3
InChIKey
GJPYYNMJTJNYTO-UHFFFAOYSA-J
PubChem
CID 24939

How the EU defines it

The legal specification an additive must meet to be sold as this E number in the EU — what it is, how it may be made, and the purity it must reach. From Commission Regulation (EU) No 231/2012.

E 521 Aluminium sodium sulphate

Synonyms: Soda alum; Sodium alum

Assay, identification and purity criteria

Description and assay

Einecs
233-277-3
Chemical name
Aluminium sodium sulphate
Chemical formula
AlNa(SO₄)₂ · nH₂O (n = 0 or 12)
Molecular weight
242,09 (anhydrous)
Assay
Content on the anhydrous basis not less than 96,5 % (anhydrous) and 99,5 % (dodecahydrate)
Description
Transparent crystals or white crystalline powder

Identification

Test for aluminium
Passes test
Test for sodium
Passes test
Test for sulphate
Passes test
Solubility
Dodecahydrate is freely soluble in water. The anhydrous form is slowly soluble in water. Both forms are insoluble in ethanol

Purity criteria

Loss on drying
Anhydrous form: not more than 10,0 % (220 °C, 16 hours) Dodecahydrate: not more than 47,2 % (50-55 °C, 1 hour then 200 °C, 16 hours)
Ammonium salts
No odour of ammonia detectable after heating
Selenium
Not more than 30 mg/kg
Fluoride
Not more than 30 mg/kg
Arsenic
Not more than 3 mg/kg
Lead
Not more than 5 mg/kg
Mercury
Not more than 1 mg/kg

Commission Regulation (EU) No 231/2012, Annex, E 521

Every name it appears under

61 recorded names. A label may use any of them.

E number

  • E521

CAS registry number

  • 10102-71-3

As it appears in regulation

  • Aluminium sodium sulphate
  • Aluminum sodium sulfate

Other names

  • ALUMINIUM SODIUM BIS(SULFATE)
  • Aluminium sodium bis(sulphate)
  • ALUMINIUM SODIUM SULFATE
  • ALUMINIUM SODIUM SULFATE ANHYDROUS
  • Aluminium sodium sulphate
  • aluminium(3+) ion sodium disulfate
  • Aluminum sodium disulfate
  • ALUMINUM SODIUM SULFATE
  • Aluminum sodium sulfate (AlNa(SO4)2)
  • ALUMINUM SODIUM SULFATE ANHYDROUS
  • Aluminum sodium sulfate, NaAl(SO4)2
  • Aluminum sodium sulfic acid
  • Aluminum sodium sulphate
  • ALUMINUM SODIUM SULPHATE ANHYDROUS
  • Aluminum sodium sulphic acid
  • E 521
  • EXSICCATED SODIUM SULFATE
  • HSDB 571
  • INS NO.521
  • INS-521
  • NATRII SULFAS EXSICCATUS
  • Soda alum
  • Sodium alum
  • SODIUM ALUM ANHYDROUS
  • Sodium aluminium sulfate
  • Sodium aluminum sulfate
  • Sodium aluminum sulfate (NaAl(SO4)2)
  • SODIUM ALUMINUM SULPHATE
  • SULFURIC ACID, ALUMINIUM SODIUM SALT (2:1:1)
  • Sulfuric acid, aluminum sodium salt (2:1:1)
  • XUANMINGFEN

Systematic names

  • aluminum sodium disulfate

Hazard reference values

Values set by assessing bodies. A body that has not set a value is not listed here.
TypeValuePopulationAssessed byOpinion
ADInot allocated—JECFA1978

Evidence and how bodies read it

What assessing bodies concluded

Each conclusion is paraphrased in the body's own framing, from the published opinion linked beneath it. Where bodies differ, both stand; this site does not adjudicate between them or add a view of its own.

  1. EFSA 2018

    The ANS Panel concluded that aluminium sulphates (E 520–E 523) and acidic sodium aluminium phosphate (E 541), which are permitted in only a few specific products with exposure probably near zero, are of no safety concern at current authorised uses and use levels.

    Source document

Common questions

Assembled from what is above, in the words the questions are usually asked in. Each answer is the same statement the relevant section makes, with the same citations behind it.

What is E 521?
E 521 is Aluminum sodium sulfate. Aluminium sodium sulfate is a firming agent and a raising-agent component in some baking powders.
What is Aluminum sodium sulfate used for in food?
It is listed as an acidity regulator, a raising agent and a firming agent — the role Canada and the US assign it. This page shows every function each regulator records, with the citation for each.
Where is Aluminum sodium sulfate permitted?
Of the seven regulators this site reads, Canada, the EU, Great Britain and the US permit it. Each permission is for named foods at named levels, not a blanket one; the table on this page gives them with citations.
Is Aluminum sodium sulfate vegan?
Yes. Aluminum sodium sulfate is not derived from animals, and is suitable for vegetarians. This page says what it is made from and how.

Sources for this page

  • ca retrieved 2026-10-17
  • eu retrieved 2026-10-18
  • gb retrieved 2026-10-18
  • ecfr retrieved 2026-10-17
  • euspecs retrieved 2026-10-18

Full licence terms and publisher details on Sources. How this page is built and updated: Method.

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