E535 - Sodium ferrocyanide

At a glance

• Role: Anti-caking agent that keeps salt free-flowing.
• Where it’s used: Table salt, sea salt, iodized salt, and sometimes salty seasoning blends.
• What it looks like: A colorless to pale-yellow crystalline solid; used at tiny amounts so it does not change the look or taste of salt.
• Label names: “E535,” “sodium ferrocyanide,” or “yellow prussiate of soda.”
• Heat and taste: Neutral in flavor; stable during normal cooking.
• Regulatory status: Authorized in the EU for use in edible salt; detailed identity and purity rules apply.¹

Why is Sodium ferrocyanide added to food?

Salt attracts moisture from the air. When the crystals get damp, they stick together and form hard lumps. Sodium ferrocyanide prevents this “caking,” helping salt stay dry, free-flowing, and easy to measure. In the European Union, E535 is authorized specifically as an anti-caking agent for food salt.¹

What foods contain Sodium ferrocyanide?

You will most commonly find E535 in:

• Table salt and cooking salt (including iodized salt)
• Sea salt and rock salt sold for the kitchen
• Some seasoning salts and premixed spice blends where salt is a main ingredient

Manufacturers usually list it on the ingredient line as “E535,” “sodium ferrocyanide,” or “yellow prussiate of soda.”

What can replace Sodium ferrocyanide?

Other anti-caking agents used for salt and dry seasonings include:

• Ferrocyanide salts: potassium ferrocyanide, calcium ferrocyanide
• Silicates and silica: silicon dioxide, calcium silicate, sodium aluminium silicate
• Carbonates: magnesium carbonates

At home, a simple non-additive workaround is to keep salt in a sealed container or add a few grains of rice to the shaker.

How is Sodium ferrocyanide made?

Food-grade sodium ferrocyanide is produced as a crystalline decahydrate with the formula Na4[Fe(CN)6]·10H2O. Its identity and purity are set in EU specifications for food additives, which include tests for composition and limits on impurities.² Chemical reference listings also describe the same decahydrate form and naming (for example, “yellow prussiate of soda”).³

Is Sodium ferrocyanide safe to eat?

In the EU, sodium ferrocyanide has been evaluated and authorized for use as an anti-caking agent in edible salt. Authorization means its uses, levels, and food categories are defined in law.¹ In addition, detailed EU specifications set identity and purity criteria (including impurity limits) that manufacturers must meet for food use.² When used as intended and within these rules, E535 does not change the taste of food and helps keep salt quality consistent.

Does Sodium ferrocyanide have any benefits?

• Keeps table salt free-flowing, so it pours and measures evenly
• Helps prevent clumps in salty spice mixes
• Improves consistency in food manufacturing where accurate dosing of salt matters

Who should avoid Sodium ferrocyanide?

• People who prefer additive-free products (for personal or culinary reasons)
• Cooks making pickles, brines, or preserves who want additive-free “canning” or “pickling” salt for clarity
• Anyone advised by a healthcare professional to avoid specific additives should check labels and follow that guidance

Myths & facts

• Myth: “It contains cyanide, so it must be dangerous.” Fact: The cyanide in sodium ferrocyanide is tightly bound to iron in a stable complex that behaves very differently from free cyanide. Its use in food salt is specifically authorized by EU law at very low levels.¹
• Myth: “It makes salt taste odd.” Fact: E535 is used at tiny amounts and is flavorless, so it does not change the taste of salt.
• Myth: “It’s a filler that bulks up salt.” Fact: It is not a filler; it’s an anti-caking aid added in minute quantities to keep salt dry and free-flowing.

Sodium ferrocyanide in branded foods

You’ll most often see E535 on labels of retail table salt and iodized salt. Some sea salts, rock salts, and seasoning salts also use it to prevent clumping. Look for “E535,” “sodium ferrocyanide,” or “yellow prussiate of soda” near the end of the ingredient list.

References

Footnotes

1. Regulation (EC) No 1333/2008 on food additives — Official Journal of the European Union. https://eur-lex.europa.eu/eli/reg/2008/1333/oj ↩ ↩² ↩³ ↩⁴

2. Commission Regulation (EU) No 231/2012 laying down specifications for food additives — Official Journal of the European Union. https://eur-lex.europa.eu/eli/reg/2012/231/oj ↩ ↩²

3. Sodium ferrocyanide decahydrate — PubChem, National Institutes of Health. https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-ferrocyanide-decahydrate ↩