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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: sherwood on October 10, 2013, 10:25:56 AM

Title: Unknown Particles in 50% Sodium Hydroxide Solution
Post by: sherwood on October 10, 2013, 10:25:56 AM

Hello,

I have several containers of 50% Sodium Hydroxide that, when opened, contained a large amount of white particles.  The material is Macron item 7705:

http://www.avantormaterials.com/commerce/product.aspx?id=4294973262 (http://www.avantormaterials.com/commerce/product.aspx?id=4294973262)

I've used this material many times in the past without issue and I'd like to determine the identity of the particles in my current lot.

I have two theories at this point:

• The particles are solid sodium hydroxide that either went undissolved during manufacture or temperatures below 60F during shipping caused some phase transition.
• The particles are sodium carbonate (Na₂CO₃) resulting from absorption of CO₂ from the container headspace

My first question is about isolation of the particles.  My initial plan was to vacuum filter the solution then wash the particles with a nonpolar solvent (I have diethyl ether available at the moment) to remove traces of the solution.  A colleague believes I should filter the solution then dry the particles in an oven.  I'm worried that residual solution will cause problems with later identity testing.

Do either of these plans have merit?  Is there a better choice?

Thanks,
Sherwood

Title: Re: Unknown Particles in 50% Sodium Hydroxide Solution
Post by: Archer on October 10, 2013, 10:37:45 AM

I would filter it and test the wet solid with a few drops of 1M HCl, that will show if it's carbonate the presence of NaOH solution will not stop the formation of CO₂