Sodium tetraborate (borax)

E number E285CAS 1330-43-4

Chemical structure of Sodium tetraborate (borax), from PubChem compound 10219853
Structure from PubChem CID 10219853 (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.

Borax is permitted in the EU as a preservative only in sturgeon caviar, sharing a combined limit with boric acid.

Where it is and isn’t permitted

Status of Sodium tetraborate (borax) 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 CanadaNo listing matchedHealth Canada’s lists name additives without E or INS numbers, so this site matches them by exact name. A substance listed there under a name this site does not recognise has no row here.
European UnionEuropean Commission / EFSAPermitted, with conditions

1 food category

highest permitted level 4,000 mg/kg

ML = 4000 mg/kg. only Sturgeons' eggs (Caviar). Note 54: Expressed as boric acid.

Regulation (EC) No 1333/2008, Annex II, as amended by (EU) No 1129/2011retrieved 2026-10-18
Great BritainFood Standards Agency / Food Standards ScotlandPermitted, with conditions

1 food category

highest permitted level 4,000 mg/kg or mg/l

ML = 4000. only Sturgeons’ eggs (Caviar). Note (54): Expressed as boric acid.

Assimilated Regulation (EC) No 1333/2008, Annex II (as at 28 June 2024)retrieved 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 AdministrationNot listedDoes not appear on this jurisdiction’s permitted list. That is not the same as being prohibited.
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.

European Union4,000 mg/kg1 numeric limit
Great Britain4,000 mg/kg1 numeric limit

What it is made from

Mined as the mineral borax from evaporite deposits and purified.

  • Vegan
  • Vegetarian

Compare other additives on the dietary indexes.

CAS registry number
1330-43-4
InChIKey
UQGFMSUEHSUPRD-UHFFFAOYSA-N
PubChem
CID 10219853

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 285 Sodium tetraborate (borax)

Synonyms: Sodium borate

Assay, identification and purity criteria

Description and assay

Einecs
215-540-4
Chemical name
Sodium tetraborate; Sodium biborate; Sodium pyroborate; Anhydrous tetraborate
Chemical formula
Na₂B₄O₇ Na₂B₄O₇·10H₂O
Molecular weight
201,27
Description
Powder or glass-like plates becoming opaque on exposure to air; slowly soluble in water

Identification

Melting range
Between 171 °C and 175 °C with decomposition

Purity criteria

Peroxides
No colour develops with added KI-solution
Arsenic
Not more than 1 mg/kg
Lead
Not more than 5 mg/kg
Mercury
Not more than 1 mg/kg

Commission Regulation (EU) No 231/2012, Annex, E 285

Every name it appears under

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

E number

  • E285

CAS registry number

  • 12267-73-1
  • 1310383-93-7
  • 1330-43-4

As it appears in regulation

  • borax
  • Sodium tetraborate
  • Sodium tetraborate (borax)

Other names

  • Anhydrous borax
  • Borax Anhydrous
  • Borax glass
  • Borax, dehydrated
  • Borax, fused
  • Boric acid (H2B4O7), disodium salt
  • Boric acid (H2B4O7), sodium salt
  • Boric acid, disodium salt
  • Boron sodium oxide (B4Na2O7)
  • Dehybor
  • DISODIUM BICYCLO[3.3.1]TETRABOROXANE-3,7-BIS(OLATE)
  • Disodium salt of boric acid
  • Disodium tetraborate, anhydrous
  • disodium;3,7-dioxido-2,4,6,8,9-pentaoxa-1,3,5,7-tetraborabicyclo[3.3.1]nonane
  • disodium;[oxido(oxoboranyloxy)boranyl]oxy-oxoboranyloxyborinate
  • Fused borax
  • Fused sodium borate
  • Granubor
  • HSDB 5025
  • INS NO.285
  • INS-285
  • Komex
  • Rasorite 65
  • Sodium biborate
  • SODIUM BORATE [MI]
  • Sodium borate, anhydrous
  • Sodium boron oxide
  • Sodium boron oxide (na2b4o7)
  • Sodium pyroborate
  • Sodium tetraborate
  • Sodium tetraborate (Na2B4O7)
  • Sodium Tetraborate, Anhydrous
  • Sodium tetraborate, anhydrous, Puratronic
  • Sodium tetraborate,Trace metals grade 99.95%
  • Sodiumtetraborate
  • Spraybor

Systematic names

  • Disodium;[oxido(oxoboranyloxy)boranyl]oxy-oxoboranyloxyborinate

The EU re-evaluation programme

Every additive authorised in the EU before 20 January 2009 was put back through EFSA by Commission Regulation (EU) No 257/2010, and this one is named in it. What the Regulation required is below; whether the opinion has since been published is not something this site records.

  • To be evaluated by 31 December 2015. Named in Annex II, Part II, point 1 as “Sodium tetraborate (borax)”, among the additives given priority within its class.

Hazard reference values

EFSA and JECFA have both assessed Sodium tetraborate (borax) and their conclusions are not two comparable figures — EFSA records 0.16 mg/kg bw/day, JECFA not allocated. An acceptable daily intake is a reference value set by a committee, not a threshold above which harm begins. “Not specified”, “not limited” and “not allocated” are conclusions, not missing data, and they are shown in the words each body used rather than reduced to a number. See where the two committees differ.

Values set by assessing bodies. A body that has not set a value is not listed here.
TypeValuePopulationAssessed byOpinion
ADI0.16 mg/kg bw/dayconsumersEFSA ANS2013
ADInot allocated—JECFA1961

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 2013

    The ANS Panel concluded that boric acid (E 284) and borax (E 285) do not raise concern for genotoxicity, but noted adverse effects on the male reproductive system in animal studies. It established a group ADI of 0.16 mg boron/kg bw/day and concluded that regular exceedance of the ADI from the authorised use in sturgeon eggs (caviar) was unlikely.

    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 285?
E 285 is Sodium tetraborate (borax). Borax is permitted in the EU as a preservative only in sturgeon caviar, sharing a combined limit with boric acid.
Where is Sodium tetraborate (borax) permitted?
Of the seven regulators this site reads, the EU and Great Britain 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 Sodium tetraborate (borax) vegan?
Yes. Sodium tetraborate (borax) is not derived from animals, and is suitable for vegetarians. This page says what it is made from and how.

Sources for this page

  • eu retrieved 2026-10-18
  • gb retrieved 2026-10-18
  • euspecs retrieved 2026-10-18

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

Machine-readable: a JSON record of this additive is given on request —how to ask for access.

Follow changes to Sodium tetraborate (borax):Atom feed — regulatory events, and any change the weekly refresh detects in its provisions.