How bleach is made

Household bleach is just salt water zapped with electricity, then mixed with its own byproduct.

stations: 7
things upstream: 24
raw sources: 10
steps from the ground: 7

The short version

Household bleach is sodium hypochlorite in water. A plant runs electric current through salty brine, which splits it into chlorine gas, hydrogen and caustic soda. Chlorine is then bubbled into cooled caustic soda solution, which captures it as hypochlorite. The solution is diluted to a 3 to 6 percent strength, checked and bottled.

Dissolve the salt

Salt from rock deposits or seawater is dissolved in water to make a saturated brine. The brine is purified to remove calcium and magnesium that would foul the cells.

Goes in
Rock salt Water
Electrolyze the brine

Brine flows through a cell divided by a membrane. Current pulls chlorine out at one electrode and makes hydrogen and caustic soda at the other. The chlorine-alkali process uses a lot of electricity per tonne of sodium hydroxide.
Collect the products

Chlorine gas, hydrogen and caustic soda leave the cell by separate pipes. Each is a commodity chemical on its own.
React chlorine with lye

Chlorine gas is fed into a chilled caustic soda solution, and the two combine into sodium hypochlorite, salt and water.

Goes in
Chlorine Caustic soda
Dilute to strength

The strong solution is diluted with water until its hypochlorite content falls in the household range. A stabilizer helps it keep for months.

Goes in
Water
Test the batch

Chemists titrate samples to confirm the strength, since bleach slowly loses potency in light and heat.
Bottle in opaque plastic

Opaque plastic bottles with vented caps are filled and labeled with warnings against mixing bleach with other cleaners.

Goes in
Plastic bottle

End of the lineBleach Next it goes into kitchen sponge.

Worth repeating

The chloralkali process uses around 2,500 kWh of electricity per tonne of sodium hydroxide produced.
Household bleach is a dilute 3 to 6 percent solution of sodium hypochlorite, historically called Labarraque's water.
In the 1820s French chemist Antoine-Germain Labarraque showed that chlorine bleach solutions slowed putrefaction, long before germ theory.