Sodium Hydroxide 1

[metrat23]

I'm trying to mix a solution of sodium hydroxide flakes in water, to achieve a concentration of about 5%. Can I verify this concentration by a hydrometer, pH or is there a titration I can use?

Any feedback would be appreciated. Thanks

 

[IRstuff]

If you only need "about" then why not just weigh the stuff before you mix it?

TTFN

FAQ731-376

 

[CoryPad]

Titration definitely will work, just use HCl and your favorite indicator, e.g.

http://en.wikipedia.org/wiki/PH_indicator

A hydrometer should work since the specific gravity of sodium hydroxide solutions does vary with concentration, see here:

http://www.dow.com/PublishedLiterat...soda/pdfs/noreg/102-00487.pdf&fromPage=GetDoc

pH is not a good option since the value will be greater than 14 for your concentration, which is outside the standard capabilities of pH meters.

 

[tomwalz]

Just an aside.

I find Caustic Pels (pellets) cleaner and easier to use.

Tom

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[cloa]

metrat23 might have a lot of sodium hydroxide in less than ideal storage i.e. it has absorbed water vapour. Maybe the weighing scales available aren't as accurate as needed and its just one off.

 

[Compositepro]

For safety add flakes slowly to water. There is significant heat released in dissolving caustic soda and a pile of it at the bottom of the container of water can easily start to boil. As for determining concentration I think weighing is easiest. Density, titration, and pH will work.

 

[tomwalz]

Composite pro brought up a good point.

I see the heating with Pels but the small, round shapes don’t seem to cause nearly as much agitation in the water as flakes.


Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[IRstuff]

Hypothetically, spheres have the lowest surface area to volume, so flakes would have more exposed surface area that would participate in any reaction with the water.

TTFN

FAQ731-376