Asked by: John Mitchell, Glasgow
The part that makes them fizz is the same as an Alka Seltzer or soluble aspirin tablet: sodium bicarbonate and citric acid. These chemicals are inert when they are dry powders, but in water they dissolve and the citric acid reacts with the sodium bicarbonate to form sodium citrate and carbon dioxide.
The sodium citrate stays in solution and you don’t really notice it, but the carbon dioxide bubbles out as a gas that helps the bath bomb break up. This lets the detergents, perfumes and oils that make up the rest of the bath bomb mix with the bathwater.
- How much salt would I need to float in my bath?
- How long does a shower have to be, to use the same amount of water as a bath?
Luis trained as a zoologist, but now works as a science and technology educator. In his spare time he builds 3D-printed robots, in the hope that he will be spared when the revolution inevitably comes.