soda and water. The chlorine and caustic soda are produced by putting direct current electricity through a sodium chloride salt solution in a process called electrolysis. Sodium chloride, common table salt, comes from either mines or underground wells. The salt is dissolved in hot water to form a salt solution, which is then treated for impurities before it is reacted in the electrolytic cell.
The Manufacturing Process
Manufacturing sodium hypochlorite bleach requires several steps. All these steps can be carried out at one large manufacturing facility, or the chlorine and caustic soda can be shipped from different plants to the reactor site.
Preparing the components
Caustic soda is usually produced and shipped as a concentrated 50% solution. At its destination, this concentrated solution is diluted with water to form a new 25% solution.
When water dilutes the strong caustic soda solution, heat is created, so the diluted caustic soda is cooled before it is reacted.
If the chlorine is manufactured outside the reactor facility, it travels in liquid form in specially designed railroad tank cars with double walls that will not rupture in the event of a derailment. Upon arrival at the plant, the liquid chlorine is pumped from the railroad cars to a holding vat.
Inside the facility, chlorine vats are housed in an enclosed area called a car barn. This enclosed room is equipped with air 'scrubbers' to eliminate any escaped chlorine gas, which is harmful to humans and the environment. The vacuum-like scrubbers take any chlorine gas from the enclosed area and injects it with caustic soda. This turns it into bleach, which is incorporated into the manufacturing process.
The chemical reaction
Chlorine and the caustic soda solution are mixed to form sodium hypochlorite bleach. To make sodium hypochlorite, liquid or gaseous chlorine is circulated through the caustic soda solution. The reaction of chlorine and caustic soda is nearly immediate.
Cooling and purifying
The bleach solution is then cooled to help prevent decomposition.
This cooled bleach is filtered to remove impurities that can discolor the bleach or cause its decomposition.
The finished sodium hypochlorite bleach is shipped to a bottling plant or bottled on-site. It is also tested to make certain it contains the correct percentage of sodium hypochlorite. Householdstrength bleach is typically 5.25% sodium hypochlorite in an aqueous solution, while swimming pool bleach is typically 10-12%.
Packaging
Sodium hypochlorite bleach was originally sold in steel containers and then in glass bottles.
The 1960s brought plastic jugs – a cheaper, lighter and non-breakable alternative. Furthermore, the thick plastic did not permit ultraviolet light to reach the bleach, which improved its chemical stability and effectiveness. Today, however, plastic containers have become an environmental concern because of the time it takes to decompose.
Many companies have begun to reduce the amount of plastic in their packaging or to use recycled plastics. In the early 1990s, Clorox introduced postconsumer resins (PCR) in its packaging. The newer bottles are a blend of virgin high-density polyethylene (HDPE) and 25% recycled plastic, primarily from clear milk jug-type bottles.
