Chapter 10: Acids and alkalis · Part 1: Alkalis
Sodium carbonate
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The worst fact: Safe Work Australia lists it as "Causes serious eye damage" (it also lists "Causes serious eye irritation", and the EU's official class is eye irritation only). The crystal form is listed as "Causes severe skin burns and eye damage".
Why brands use it: it softens water and cuts grease and dirt cheaply.
Take care if: you have children, or for your eyes. In Australia, carbonate, silicate and phosphate "alkaline salts" are a Schedule 5 Poison in solid products whose pH at 10 g per litre is above 11.5 (dishwasher powders are tested at a much stronger 500 g per litre), and in liquids above pH 11.5. Washing soda on its own falls just under that line (a 1% solution measures pH 11.37), so a box of washing soda or a typical laundry powder isn't usually scheduled.
Comes from: a natural mineral (trona) or salt brine, or made from salt and limestone (the Solvay process, about 70% of world capacity).
Myth check: "Natural cleaners like washing soda are harmless": no. It's a much stronger alkali than bicarb. Natural doesn't mean gentle.
Contaminants: nil.
Fair to say: on healthy, unbroken skin it caused no reaction in a human patch test. The danger is to eyes, mouths and broken skin.
We use this ingredient. It's in our Laundry Powder and Dishwasher Powder, as an alkaline builder that lifts grease and food. Both are powders you scoop into a machine. Keep the powder away from children and out of your eyes.
Correct as of November 2026. What the badges mean
Sources
- Australian Government. Poisons Standard October 2026 (SUSMP), F2026L01327: sodium hydroxide, potassium hydroxide, alkaline salts, monoethanolamine, sulfamic acid, hydrochloric acid, acetic acid; Appendix B (sodium bicarbonate).
- Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for each chemical, and for ethylene oxide, carbon monoxide and acetaldehyde.
- HSDB (US National Library of Medicine), via PubChem: production and impurity data for each chemical.
- Kilah N. Cleaning with vinegar and baking soda. The Conversation, 2024.
The full source list is at the end of Chapter 10.