Bleach Facts (Answers to Common Questions)

Bleach Facts (Answers to Common Questions)

Answers to Common Questions About the Everyday Chemical

By Anne Marie Helmenstine, Ph.D.

Updated February 23, 2018

Bleach is the common name for a solution of 2.5% sodium hypochlorite in water. It's also called chlorine bleach or liquid bleach. Another type of bleach is oxygen-based or peroxide bleach. While you may know bleach is used to disinfect and remove stains, there is more to know about this everyday chemical to use it safely and effectively. Here are some important facts about this solution.

Useful Bleach Facts

• Bleach has a shelf life and expiration date. On average, a container of unopened bleach loses 20% of its effectiveness each year. Once opened, bleach starts to lose a significant amount of its power after 6 months.

• Chlorine bleach is more effective as a disinfectant when it's diluted rather than if it's used at full strength. A typically recommended dilution is 1 part bleach to 9 parts water.

• A higher percentage of bleach is needed if a large quantity of organic material (e.g., blood, protein) is present, as these materials react with bleach and tend to neutralize it.

• If you add sodium hypochlorite bleach to whiten laundry or remove stains, it's better to add it after the wash cycle has already filled with water and started agitation. If you add bleach together with detergent, you risk diminishing the effectiveness of enzyme-based stain removers and the detergent. On the other hand, oxygen-based bleach is best added to warm or hot water before clothes are added. Oxygen-based bleaches are generally color-safe and will preserve whiteness, but will not remove color. Sodium hypochlorite bleach does whiten fabrics but is not safe for all materials.

• Bleach reacts with several other chemicals to release toxic vapors. It's generally inadvisable to mix bleach with other cleaners. In particular, avoid mixing bleach with acetone, alcohol, vinegar or other acids, or ammonia.

• Bleach can corrode metal, so if you clean or disinfect a metal surface with bleach, it's important to wipe it down with water or alcohol afterward.

• Although it's commonly believed drinking bleach can lead to a negative blood or urine test for drug use, this is untrue.

• While chlorine bleach is a powerful disinfectant, peroxide bleach is not suitable for this purpose. Chlorine bleach disinfects because it is an oxidizer, capable of disrupting microbial cells. Oxidation is also how chlorine bleach removes color. Sodium hypochlorite breaks bonds in the chromophore or colored portion of a molecule, rendering it colorless. Reducing bleaches also exist, which also change chemical bonds and alter how a molecule absorbs light.

• Chlorine bleach was first used to disinfect water in 1895 for New York City's Croton Reservoir.

• Household bleach may be made using water, caustic soda, and chlorine. The process of electrolysis is used to produce chlorine and caustic soda by running an electric current through a solution of table salt (sodium chloride) in water. Caustic soda and chlorine react to form sodium hypochlorite. All that is needed is to bubble chlorine gas through caustic soda solution. Since chlorine gas is toxic, bleach is not a chemical one should make at home.

• Although the odor of chlorine is apparent in bleach, when bleach is used, the chemical reaction tends to produce salt water and not chlorine gas.