On Thursday, 5 April 2012 10:30:37 UTC+1, Rod Speed wrote:
stuart noble wrote
Rod Speed wrote
stuart noble wrote
Martin Brown wrote
Chris Holford wrote
Fredfred@no- email.here.invalid wrote
Chris Holford wrote

I've tried a plunger, and tried
neutralising with spirits of salts

Still waiting for the NaOH to dissolve!

Does water drain away at all? If so your only remaining option is to risk adding very hot water and hope that it
will solvate the
caustic. Repeat hourly until the thing runs free again.

Wear eye protection and if possible a full face shield.

Otherwise you are down to a dismantling job. Next time make up the solution carefully from the solid and pour it
down the plug hole!
(again eye protection essential it gets pretty hot when dissolving)

I reckon most people are better off with one of the proprietory
drain cleaners since it avoids pitfalls like this one with overdose of the solid causing a worse problem than the
fault it was trying to fix.

I've never known it take this long to dissolve, even when it has formed a solid lump. I used to have a tank of the
stuff so I know a little about its behaviour.

He did however attempt to neutralise it with HCl, so its
almost certainly the resulting NaCl thats not dissolving now
so your experience isnt that relevant to the rate it dissolves at.

But it has to have dissolved in order to be neutralised.

Nope. Whats happened is that some of the chunk of NaOH
has got turned into NaCl around the outside of the chunk
and that is considerably less soluable than the NaOH.

Otherwise the acid would at least partially wash over it

Yes, thats likely whats happened too.

So the considerably more soluble sodium hydroxide failed the acid test and is now encased in sodium chloride which is even less soluble?