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Sodium Hydroxide

Sodium Hydroxide

Sodium Hydroxide

(OP)
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

RE: Sodium Hydroxide

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/PublishedLiterature/dh_0076/0901b80380076460.pdf?filepath=causticsoda/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.

 

RE: Sodium Hydroxide

Just an aside.

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

Tom  

Thomas J. Walz
Carbide Processors, Inc.
www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.    

RE: Sodium Hydroxide

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.   

RE: Sodium Hydroxide

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.  

RE: Sodium Hydroxide

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.
www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.    

RE: Sodium Hydroxide

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

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