On Tue, 20 Dec 2005 03:41:27 +0000 (UTC), John wrote:

"The Natural Philosopher" wrote in message
.. .
On Sat, 17 Dec 2005 17:03:50 GMT, david lang wrote:

The Natural Philosopher wrote:

Then copious flushing with more hot water, followed by gallons of
cold, and maybe a bit of vinegar to neutralise the alkali,..

Sorry, not having a pop at you, but it always makes me laugh when this
idea
is given as a 'trick of the trade' on DIY makeover shows, usually in
connection with stripped pine doors.

Apart from the presenters invariably not knowing their acid from their
alkali and getting it the wrong way round.

You can have no idea of how alkaline the residue is, therefore you can
have
no idea how much acidity is required to neutralise it. Caustic soda
having
a pH of around 13 and vinegar about 2 probably means you would have to
soak
the door in vinegar for a fortnight - which could leave an alkali residue
you would have to neutralise with........

Show me a TV presenter with some Litmus paper or some indicator solution
and
it might make sense.

Dave


I think yiouy are unfair.
Firstly this is a drain, not a door. One really simply wants to reduce
localised PH from dangerous (to plastisc) levels..not neutralise the PH of
th whole sewage system. Theres enough awtaer coming in from toilets and
showers and baths to dilute teh alkali to very high degrees.

Seecondly, when using caustics, on wood you wash off the bulk of the
alkali
with water. The vinegar is simply to neutralised the very little that is
left.

If you are worried about realtive Ph, Use brick acid instead.


I used to have a chart given out with one of the process plant magazines
each year which showed a selection/suitability chart for materials used with
various reagents. AFAICR it showed pvc pipe to be perfectly suitable for use
with 36% HCl and (not at the same time) 40Twaddle Caustic soda so your
dangerous to plastic comment seems a long way from the mark

Well, I had a plastic sink, and it used to pickup up a LOT of tea stains,
and I used caustic to remove em.

After a few years it was brittle and flaky on the surface. Like non U PVC
gets in sunlight.

It may not have been PVC, but it definitely degraded.