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Wash bottles are sealed with a screw-top lid. When hand pressure is applied to the bottle, the liquid inside becomes pressurized and is forced out of the nozzle into a narrow stream of liquid.
Most wash bottles are made up of polyethylene, which is a flexible solvent-resistant petroleum-based plastic. Most bottles contain an internal dip tube allowing upright use.
Wash bottles may be filled with a range of common laboratory solvents and reagents, according to the work carried out in that lab. These include: deionized water, detergent solutions and rinse solvents such as acetone, isopropanol or ethanol. In biological labs it is common to keep sodium hypochlorite solution in a wash bottle to conveniently disinfect unneeded cultures.