03-13-2012 07:22 PM
This has been tested and it is found that sodium thiosulfate does a better job of deactivating the sodium hypochlorite than the hydrogen peroxide does.
4 NaClO + Na2S2O3 + 2 NaOH → 4 NaCl + 2 Na2SO4 + H2O
A 1-in-5 dilution of household bleach with water (1 part bleach to 4 parts water) is effective against many bacteria and some viruses, and is often the disinfectant of choice in cleaning surfaces in hospitals (primarily in the United States). The solution is corrosive, and needs to be thoroughly removed afterwards, so the bleach disinfection is sometimes followed by an ethanol disinfection
Sodium hypochlorite is a strong oxidizer. Oxidation reactions are corrosive, solutions burn skin and cause eye damage, in particular, when used in concentrated forms. However, as recognized by the NFPA, only solutions containing more than 40% sodium hypochlorite by weight are considered hazardous oxidizers. Solutions less than 40% are classified as a moderate oxidizing hazard (NFPA 430, 2000).
Household bleach and pool chlorinator solutions are typically stabilized by a significant concentration of lye (caustic soda, NaOH) as part of the manufacturing reaction. Skin contact will produce caustic irritation or burns due to defatting and saponification of skin oils and destruction of tissue. The slippery feel of bleach on skin is due to this process.
Sodium thiosulfate (thio) is an effective chlorine neutralizer. Rinsing with a 5 mg/L solution, followed by washing with soap and water, quickly removes chlorine odor from the hands.
Mixing bleach with some household cleaners can be hazardous. For example, mixing an acid cleaner with sodium hypochlorite bleach generates chlorine gas. Mixing with ammonia solutions (including urine) produces chloramines.
NH4OH + NaClO → NaOH + NH2Cl + H2O
H2O2(aq) + NaClO(aq) → NaCl(aq) + H2O(l) + O2(g)
It is estimated that there are about 3300 accidents needing hospital treatment caused by sodium hypochlorite solutions each year in British homes (RoSPA, 2002).
One major concern arising from sodium hypochlorite use is that it tends to form chlorinated organic compounds; this can occur during household storage and use as well during industrial use. For example, when household bleach and wastewater were mixed, 1-2% of the available chlorine was observed to form organic compounds. As of 1994, not all the byproducts had been identified, but identified compounds include chloroform and carbon tetrachloride. The estimated exposure to these chemicals from use is estimated to be within occupational exposure limits.
Good neutralizers for chlorine
There are three good alternatives for neutralizing hypochlorite bleach: bisulfite or metabisulfite, thiosulfite, or peroxide.
Bisulfite and metabisulfite
Bisulfite, or metabisulfite, is the most economical choice. It is widely sold under the name Anti-Chlor by dye suppliers. It does not matter whether you buy sodium bisulfite or potassium bisulfite. It is economical because only small amounts are required. If your dye supplier sells anti-chlor, be sure to order some the next time you order dyes.
Bisulfite is also used as a preservative of fresh and dried foods, such as the potato salad in restaurant salad bars, or dried apricots. A good local source would be your local home wine brewing supply store, as sodium bisulfite is widely used for sanitizing the fruit juices to be used in wine, to stop yeast growth, and as a preservative. Camden Tablets are a product sometimes used in wine-making; each tablet contains 1/16th teaspoon (0.3 ml) of sodium bisulfite.
Here is the chemical equation describing the neutralization reaction between sodium hypochlorite and sodium metabisulfite:
Na2S2O5 + 2NaOCl + H2O —> 2NaHSO4 + 2NaCl
An alternative reaction is as follows:
Na2S2O5 + 2NaOCl + H2O —> 2Na2SO4 + 2HCl
Sodium thiosulfate, also known as Bleach Stop, is another excellent choice for neutralizing chlorine bleach. It is less economical than Anti-chlor because you must use a much larger quantity to prepare your bleach neutralizing bath. Thiosulfate is commonly used in developing photographs, so you may be able to find a local supplier in the form of a photography supply store. The reaction between thiosulfate and hypochlorite is as follows:
4 NaClO + Na2S2O3 + 2 NaOH → 4 NaCl + 2 Na2SO4 + H2O
Hydrogen peroxide is a third choice, perhaps preferable for asthmatics who are sensitive to the effects of sulfur-containing chemicals. It is more expensive than Anti-chlor or Bleach Stop, but it has the advantage of being readily available at pharmacies. Look for 3% hydrogen peroxide among the first aid supplies at your local drug store. The chemical reaction between hypochlorite (the active ingredient in chlorine bleach) and hydrogen peroxide is as follows:
OCl- + H2O2 -> Cl- + H2O + O2
08-20-2012 08:05 AM
Covidien has signed a contract for exclusive rights to Surface Safe. We hope to launch this product by the end of next month. Please do not hesitate to contact me if you have any questions or need any further information.
12-06-2012 07:06 AM
Surface Safe is available! It can be purchased directly through Covidien and most distributors/wholesalers. Please send me an email and I will put you in contact with your account rep so they can get your pricing set up.
12-06-2012 07:07 AM