[Histonet] Bleach as Cleaning Agent or Decontamination-

[John Kiernan]

You need to be clear about what the concentration means. Household bleach (such as Javex or Clorox) is a 5% aqueous solution of sodium hypochlorite (NaClO). Sometimes it also contains a polymer (not named on the label) to increase the viscosity.

Solutions for adding to swimming pools are 10% aqueous sodium hypochlorite and are cheaper (per gm of NaClO) than household bleach. These pool disinfectants are often labelled "liquid chlorine", a deceptive name that fosters ignorance among those who didn't pay attention at school. Chlorine boils at -34C at atmospheric pressure and exists as a liquid at ambient temperatures only when compressed in railroad tanks or in the (much smaller) gas shells used as weapons by both sides in the First World War. 

Dakin's solution, used for cleaning dirty wounds, is 0.45-0.50% sodium hypochlorite, made by dilution with a carbonate-bicarbonate buffer to reduce alkalinity. A stronger solution could be used for non-living surfaces.

Aqueous solutions of NaClO are "remarkably stable" but the solid compound is extremely unstable. The crystaline pentahydrate melts at 18C and is decomposed by reaction with carbon dioxide from the air;. Anhydrous NaClO is obtainable only by freeze-drying and is "very explosive". Nobody uses the solid. The solutions are made by reaction of chlorine (gas) with aqueous sodium hydroxide solutions. This can also be done by electrolysis of a sodium chloride solution between inert electrodes. 

My sources of information are bleach bottle labels (small print) and the Merck Index 12th edition, 1996, checked today. Every lab should have a Merck Index on the shelf of reference books! 

The phrase "99.9% commercial bleach" could not possibly mean 99.9% of either NaOCl or its pentahydrate (solubility 29%). 5.25% (absurd precision!) and 10% bleach probably mean volume dilutions (1:20 or 1:10) of a household hypochlorite bleach without added thickener. 

A swimming pool 10% sodium hypochlorite solution probably is the cheapest source of chlorine bleach disinfectant without unwanted additives. Dilute it 10-20X with water to swab your possibly infected surfaces. Beware of lab supply companies selling household products at greatly inflated prices. Anyone purporting to sell "hospital grade premade bleach" needs to be viewed with much suspicion. 

Think before you buy.

John Kiernan
London, Canada
= = =
On 08/05/15, ian bernard  <ian.bernard at comcast.net> wrote:
> Our facility is moving towards standardization of decontaminants or
> disinfectants. They prefer all areas use a Sani wipes that kills most
> pathogens.
> 
>  
> 
> However, we contend for Anatomic pathology we need our liquid bleach not
> only as disinfectant or decontaminant but as a cleaning agent for stained
> lab-ware. You thoughts?
> 
>  
> 
> Also, what concentration of Bleach (5.25 or 10%) is acceptable for use as
> both a disinfectant and cleaning agent or should we keep them separate? 
> 
>  
> 
> We used to buy the hospital grade premade bleach at a 5.25% concentration
> but now they want us instead to buy the 99.9% commercial Bleach and dilute
> from there. Any suggestions on opaque containers for us to purchase since
> bleach break down after a time period, at least for disinfecting?
> 
>  
> 
> V/r
> 
> IB
> 
>  
> 
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