[Histonet] Tap Water in Staining

John Kiernan jkiernan <@t> uwo.ca
Thu Dec 8 08:38:40 CST 2005

Distilled or deionized ("pure") water nearly always has a pH
between 5 and 6 because of dissolved carbon dioxide (carbonic
acid) from the air. To change the colour of haemalum-stained
nuclei from red to blue the pH should be 7 or higher. Hard tap
water is neutral or slightly alkaline, and the dissolved calcium
bicarbonate can serve as a buffer. A drop of anything alkaline
will bring the pH of pure water 
to a little over 7. I use limewater (saturated, that's about
0.3%, aqueous calcium hydroxide) because Ca(OH)2 is harmless and

John Kiernan
Anatomy, UWO
London, Canada
"Parker, Helayne" wrote:
> In using tap water for an H & E stain is there any documentation or
> testing that needs to be done to confirm that the tap water is ok for
> use.  They have been using DI water here and there were complaints of
> slides being too pink from the Pathologist.  I put the tap water into
> the regimen instead as I have always used tap for H & E staining -color
> is now fine - no problems.  But I was asked by the other tech is that
> was acceptable.  Having never been a supervisor I am not aware of any
> documentation needed. Can anyone advise.
> Helayne Parker, HT (A.S.C.P.)
> Histology Section Head
> Skaggs Community Health Center
> Branson, MO
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