Re: 10% Bleach

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From:Mick Rentsch <> (by way of histonet)
To:histonet <>
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Dear Greg,
you are likely to find official guidelines through the American Bloold
Banking Assoc., Immunohaematoloogy Discussion Groups etc.
First a few points:- Conc. Sodium Hypo is available about 12.5% w/v at time
of manufacture and with or without up to 4% Potassium or Sodium Hydroxide.
The hydroxide formulations are often rated at 5%, and these are usually
quite stable and deteriotate little over twelve months- this is the common
houshold Domestos or whatever the local brand. The stronger commercial
solutions loose about 1% content per fortnight downwards  from 13% . and so
must be used as fresh as possible (ie within 4 weeks) this is the type used
by Industry, water authorities, dairies etc.
For practical purposes of use treat domestic bleach (Stabilised ) as being
5% even if label says 10% esp. if material is more than four months old
(After four months decay rate slows down -don't know why).
Your working solution should be diluted to about 10,000ppm of available
Chlorine, you will need to replace every 2-3 days (say Mon & Wed. for
routine purposes) as the diluted form no longer has enough Hydroxide to
stabilise it.
Ref."Infection Control in the Health Care Setting" Apr.1996 Guidelines
----Original Message-----
From: greg tesdall <>
To: <>
Date: Friday, 13 November 1998 10:45
Subject: 10% Bleach

>Information needed. Countertops in the general Lab(Hemo, B. Bank,
>Chemistry) are cleaned at the end of each shift with a 10% bleach
>solution. They make the solution up fresh each day.  I need references
>or guidelines for the following: 1) Is it necessary to make fresh each
>day. What is the shelf life. 2) What if they were to use opaque
>bottles.  Would shelf life be longer. Any other input appreciated.
>Greg Tesdall, NE.
>Get your free address at

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