Why Does Bleach Turn Yellow?
The natural colour of bleach is colourless, however over time it can turn yellow. Bleach exposure to air, light, and heat are all responsible for the yellowing and degradation of the bleach. To understand the yellowing of bleach better, let’s break down what occurs when bleach and these three environmental sources interact.
BLEACH + AIR = YELLOW
Bleach is naturally reactive to air, meaning the oxygen in the air can combine with the hypochlorite ions in bleach and create hypochlorite salts. When this reaction occurs, the products tend to be yellow in colour.
BLEACH + LIGHT = YELLOW
Similar to oxygen, ultraviolet light also reacts with bleach. When UV radiation shines on bleach, the hypochlorite ions break up and form a variety of different compounds. Again, these compounds can be yellow in colour.
BLEACH + HEAT = YELLOW
Heat is also a factor in the degradation of bleach. Heat will cause the active chemicals in bleach to evaporate, rendering the bleach inactive. In addition, heat will cause the compounds in bleach to react with each other, forming compounds that may be yellow in colour.
The Takeaway
The takeaway is that while bleach is initially colourless, it reacts with oxygen, ultraviolet radiation, and heat. The reactions between bleach and these three environmental sources are responsible for the yellowing of bleach. Therefore, when purchasing and storing bleach, it is important to remember to keep it away from oxygen, light, and heat in order to prevent yellowing and degradation.
Tips on How to Store Bleach:
- Keep bleach in a cool, dry place away from direct light
- Do not leave bleach exposed to air
- Store bleach in a container with an air tight lid
- Keep bleach away from sources of heat
2. How long does bleach typically take to start turning yellow?
Bleach typically starts to turn yellow within 24 to 48 hours, depending on the concentration and quality of the bleach.
4. How much longer does unopened bleach last compared to bleach that has turned yellow?
Unopened bleach typically has a shelf life of between 1 – 2 years, while bleach that has turned yellow is likely no longer effective and should be discarded.
5. How can the yellowing of bleach be prevented?
The yellowing of bleach can be prevented by storing it in a cool, dry, dark place, away from direct sunlight and also using it within a few months of purchase. Additionally, using a chlorine stabilizer in the washing cycle will help prevent yellowing of bleach.
3. Is yellowing of bleach caused by oxidation?
No, yellowing of bleach is caused by chlorine gas interacting with the components in most colored fabrics. Oxidation is the term used to describe a chemical reaction involving the transfer of electrons from one species to another, usually resulting in a color change in the molecules involved in the reaction.
1. What chemicals in bleach cause it to turn yellow?
Chlorine compounds found in bleach break down upon exposure to light and heat and form yellow colored compounds known as halogenated compounds. The most common halogenated compounds found in bleaches are hypo-halites, such as sodium hypochlorite and calcium hypochlorite, as well as halogen oxides and chlorinated compounds, such as chlorine dioxide and dibromide.