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Author: Subject: High Purity Cleaning - AKA Do my work for me!
BromicAcid
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wink.gif posted on 7-3-2011 at 19:24
High Purity Cleaning - AKA Do my work for me!


Recently I became part of an elective group at my work to re-evaluate our method of high purity cleaning. The goal is to reduce leach-able trace metal content in soda-lime glass to the smallest quantity possible (leached with water targets are in the single digit PPB range). The glass will be to hold chemicals to 7-9's purity (99.99999%). I did some cursory internet searches since this just came up recently but didn't come up with much of anything useful.

I have plenty of ideas in my head already, acids, bases, fluoride solutions, chelating agents, etc., but does anyone have a procedure in literature or the like that they might be able to share. Sorry I can't give exact details such as the main contaminants and such but as this is the company I work for I am not sure what is proprietary information.




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spirocycle
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[*] posted on 7-3-2011 at 19:41


in the gold purification thread there was mentioned methods of bringing purity up to 4 or 5 decimal places.
maybe there would be some useful information there.
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hiperion42
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[*] posted on 8-3-2011 at 00:39


I doubt trace metal element content in soda-lime glass to be proprietary corporate information.




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Arthur Dent
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[*] posted on 8-3-2011 at 10:08


This is an interesting subject to me, because I recently acquired a very nice collection of glassware (bought used, origins unknown, from many defunct labs), and after a thorough wash, everything looks spotless!

But is it? I am planning to use some of this glassware for distillation of spirits, and preparation of food-grade compounds for my endeavors in home-brewing and molecular cuisine.

So any OTC cleaning process that will make my glassware useable for human foor preparation and comnsumption is certainly something i'll do. We're talking all-pyrex/kimax/chemglass ground glass equipment that includes boiling flasks, claisen adapters, condensers, thermometers and other glass accessories.

I have avoided so far using my glassware for anything that has to do with food/brewing, but I do have a set of 600 ml berzelius beakers (bought new) that I use as beer glasses when I have people over (yeah, I'm a a science geek!) LOL

I certainly don't want to contaminate my pasta with cadmium and my onion soup with cyanide, even if they are traces... Right now, the best I can do is use conc. sulphuric acid with a bit of H<sub>2</sub>O<sub>2</sub> and I do it one piece of glassware at a time (which is time consuming, but does a splendid job so far).

I use the cheap rooto H<sub>2</sub>SO<sub>4</sub> for my bath because I don't want to use my lab grade acid for that purpose. So hard to get the good stuff these days!

But back to the original poster, even in the synthesis of non-food chemicals, it would be interesting to have techniques to ensure perfectly clean glassware, especially when dealing with lead, iron, nickel and other metals that can affect a delicate experiment even in ppb trace quantities... and a technique using OTC chemicals, that would be real spiffy! :D

Robert






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vulture
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[*] posted on 8-3-2011 at 11:38


I would say something like that is close to impossible with soda-lime glass, given the mobility of sodium ions in it is appreciable. This is one of the reasons pH electrodes work with soda lime glass.



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[*] posted on 8-3-2011 at 11:43


I agree with Vulture. They make equipment from fused quartz for a reason.
Repeated leaches with hot nitric acid will probably get down to a surface that's nearly pure silica, but it will bae as absorbent as anything so it won't stay clean
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[*] posted on 8-3-2011 at 11:47


There are procedures out there to make glass surfaces hydrophobic, IIRC it involves treatment with dichlorodimethylsilane. This could make borosilicate glass suitable for your application.

Sigma-Aldrich should have some technical literature on this.




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