A GREAT DISINFECTANT BUT WE MUST LEARN THE DIFFERENCE BETWEEN sodium hypochlorite i.e.HOUSEHOLD BLEACH and calcium hypochlorite DRY CHLORINE TABLETS AND POWDE Dr.Leon Buchan PhD Microbiology, Control Chemicals LTD Robert J.Saldivar, MS Animal Science, Sanitation Specialist, Texas A&M University 1958
Calcium Hypochlorite tablets when mixed with water produce a FRESH hypochlorite solution, used as it is being produced BLEACH often called chlorine bleach a sodium hypochlorite solution us containing LYE is manufactured at a factory stored, shipped to distribution centers, stored again and then sold.
According to all the technical literature, depending on storage conditions; all hypochlorite solutions will lose half of their potency in less than thirty days.Light, temperature and age are the biggest factors.
We must also recognize that the word bleach means to whiten, and it does not mean it contains chlorine.There are many bleaching agents that do not contain any chlorine at all and are still called bleach.
web site of the Clorox company says CLOROX BLEACH
IS NOT CHLORINE, EVEN THOUGH SOME CALL IT CHLORINE BLEACH IT CONTAINS NO MORE CHLORINE THAN COMMON TABLE SALT 1998, The Clorox Company
There are three main and distinct differences between calcium hypochlorite and sodium hypochlorite often called "chlorine bleach"
1 Dry calcium hypochlorite tablets produce a " hypochlorite solution when mixed with water.In tests done, a solution produced with the proper calc hypochlorite tablet, can maintain free available chlorine or HOCl the active disinfectant in a chlorine solution, for about 4 hrs, then it starts rapidly degrading.There are many dry chlorine dispensers available
The biggest misconception is that liquid household bleach (sodium hypochlorite) does not loose potency until you make a sodium hypochlorite solution; liquid household bleach is already a sodium hypochlorite solution, that starts degrading soon after manufacture, so a "bleach" bottle bought at a retail store or chemical supply house is, NOT A FRESH HYPOCHLORITE SOLUTION it is a hypochlorite solution with an unknown chlorine content, so when we make a solution all we are doing is diluting an already weak hypochlorite solution even more.
All literature recommends that if you are using chlorine bleach, daily tests should be conducted by a laboratory to assure its potency.
2 - For a chlorine solution to be a good disinfectant it must meet the Chlorine Demand.The chlorine demand is the amount of FREE AVAILABLE CHLORINE, or (FAC) often called HYPOCHLORUS ACID or HOCl, needed to disinfect or oxidize organic matter before a FAC residual is reached.If the chlorine demand is not met then complete disinfection has not been obtained.One of the best signs that the Chlorine Demand has not been met is the strong chlorine odor present produced by chloramine gas.HOCl (hypochlorus acid), is the most germicidal of all chlorine compounds, between 80 and 120 times stronger than the OCl ion.
(Kapoor University of Illinois.
Fair, G.M.Harvard University) The pH of the solution is the determining factor on which species of chlorine is produced in the solution, HOCl or OCl- ideal pH of a disinfecting chlorine solution is a pH of 6 to 8.
Most FRESH CALCIUM HYPOCHLORITE solutions have a pH of between 7and 8, ALL (fresh or old) SODIUM HYPOCHLORITE solutions,
bleach) unless buffered by the injection of an acid, have a pH of 10.25+ producing no HOCl.These solutions produce only the OCl- ion, a very poor disinfectant which is from 80 to 120 times less effective as a disinfectant than HOCl, providing that there is any chlorine left in the stock solution.
There is a big misconception that an EPA REGISTRATION means that product is APPROVED by EPA.
According to the EPA web site the registration means that, All pesticides, (disinfectants are pesticides), sold or distributed in the USA must be registered by EPA, based on scientific studies showing that they can be used without posing unreasonable risks to people or the environment.
REFERENCES George Clifford White, Handbook of Chlorination and Alternative Disinfectants.
Third Edition, Van Nostrand Reinhold, New York, 1999
Dychdala.Chlorine and Chlorine Compounds.In: Block SS, ed.Disinfection, Sterilization, and
Preservation, 5th ed.
Philadelphia Lippincott Williams & Wilkins, 2001.
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