Washing Soda (Sodium Carbonate): Uses and Safety

Washing soda is sodium carbonate, the sodium salt of carbonic acid. In many Indian homes it's simply called dhone ka soda (धोने का सोडा). Industry knows the dry form as soda ash. It is a stronger alkali than baking soda (sodium bicarbonate), so don't swap one for the other in recipes.

• Formula: Na2CO3 (anhydrous). The older crystal form, washing soda crystals, is the decahydrate Na2CO3·10H2O.
• CAS number: 497-19-8 (anhydrous); 6132-02-1 (decahydrate)
• Molar mass: about 106 g/mol anhydrous, 286 g/mol decahydrate
• Appearance: white, odourless powder that slowly absorbs moisture from air
• Melting point: about 851 °C (anhydrous)
• Solubility: dissolves well in water, roughly 30 g per 100 mL at room temperature. The solution is strongly alkaline, around pH 11.

Azlok sells washing soda as a household and utility grade powder for laundry and cleaning. It isn't sold as food or lab grade. Pack sizes are 250 g, 450 g and 1 kg.

Compare today's price per kg across the three packs.

• Laundry: softens hard water so detergent lathers and rinses better. Useful on heavily soiled cotton, towels and kitchen dusters.
• Kitchen and home: cuts grease on kadhais, gas stove grates, exhaust fan blades and oily tiles. Also used to clear greasy sink drains.
• Dyeing and craft: fibre-reactive dyes on cotton need an alkaline soak, and soda ash is the usual fixer for tie-dye.
• Soap and detergent: a builder in detergent powders and some handmade soap recipes.
• Industry: glass making is the biggest use. It's also used in paper, textiles, water treatment and swimming pools to raise pH.

Always dissolve washing soda in water first. Dry powder can leave white patches on dark clothes.

1. Bucket wash: dissolve 1 to 2 tablespoons (about 15–30 g) in a bucket of warm water, add your usual detergent, and soak whites or towels for 30 minutes before washing.
2. Washing machine: add 1 to 2 tablespoons to the detergent drawer along with detergent for a normal load in hard water. Check your machine's manual first.
3. Greasy utensils and grates: dissolve about 2 tablespoons in 1 litre of hot water. Soak for 15–30 minutes, scrub, then rinse well.
4. Drain: pour about half a cup of powder into the drain, follow with a kettle of hot water, and flush with more water after 15 minutes.
5. Tie-dye: follow the dye maker's soak ratio, since dyes differ.

Don't use it on aluminium vessels, wool, silk, leather, wood finishes or non-stick coatings. Alkali dulls or damages them.

• Washing soda is alkaline and can irritate skin and eyes. Wear rubber gloves for soaking and scrubbing. Rinse hands afterwards.
• If it gets in the eyes, rinse with clean running water for several minutes and get medical help if irritation stays.
• It is not for eating or cooking. Keep it out of the masala shelf so nobody mistakes it for baking soda.
• Don't mix it with acids, vinegar or toilet acid cleaners. It fizzes and releases carbon dioxide, and the cleaning effect cancels out.
• Store it in a closed, labelled container in a dry place. It absorbs moisture and forms lumps.
• Keep away from children and pets.
• Household amounts diluted in plenty of water can go down the drain.

For laundry, cleaning and dyeing, the household grade powder is all you need. Paying for a lab grade adds nothing for these jobs. Start with the 250 g or 450 g pack if you're testing how much your water needs. Families who wash daily in hard-water areas usually go through a 1 kg pack quickly and get a better per-kg price.

Laundries, dyeing units, soap makers and cleaning businesses that need 25 kg or more should ask for a quote through bulk inquiry. Mention whether you need light or dense soda ash.