From: Mark Potyen <mark.potyen**At_Symbol_Here**SIAL.COM>
Subject: Re: [DCHAS-L] Pyrophorics
Date: Fri, 25 Sep 2015 13:22:53 -0500
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: CAH=A9_fwxfxuZ9u+JFGRtYSsfzHasWX98FMZZssWA54xH4g15Q**At_Symbol_Here**
In-Reply-To <009c01d0f7ab$b25222e0$16f668a0$**At_Symbol_Here**>

We used alkylaluminium materials daily in our lab. Our glove boxes have constant monitoring of both oxygen and moisture. Oxygen is rarely a problem, usually below 0.2ppm. What we run into is a problem with moisture. The catalyst and sieves cannot keep up on humid days and the moisture content in the one of our boxes can creep up to 1.0ppm towards the end of the day with constant use. At that point, we need to purge the box before using it. At 0.7ppm water most alkylaluminium materials will fume inside the dry box. When I was doing work into detecting oxygen in organometallic materials at the ppm level I need to have the box below 0.2ppm oxygen and 0.5ppm water. However, this is not on the safety side this is to avoid contamination with our high purity electronics grade materials.

In graduate school we used dimethyl zinc to test the box atmosphere and to indicate when we needed to regenerate the catalyst and sieves. If it fumes we regenerated the catalyst. In a box without an atmosphere scrubber we used a pan of sodium-potassium alloy to keep the atmosphere dry. We would scrape off the top layer and expose a fresh layer of the liquid to dry the atmosphere.

Sorry but we do not have any hard and fast rules for the safety in the glove boxes we have to worry about oxygen contamination well before that point and for those (both moisture and oxygen) we work if it is 1ppm or more but that was an arbitrary number that was picked. I have heard that a fire could occur at 200ppm of oxygen but that I would guess it would be short lived unless it had a constant source of oxygen. I do not know if that is true I have never seen a fire in a glove box only a glove bag and I had no idea how much oxygen was in the glove bag. I hope any of this helps.

Mark Potyen

On Fri, Sep 25, 2015 at 11:03 AM, NEAL LANGERMAN <neal**At_Symbol_Here**> wrote:


Thank you for the initial response; you have confirmed what I noted- the data do not seem to be available.

Allow me to change the question-

Some facts:

The specification for oxygen in cylinder nitrogen is less than 200 ppmv and it goes down as the quality of the nitrogen goes up. Semiconductor grade is < 3 ppmv.

If you were monitoring the oxygen concentration inside a glove box (containment) using nitrogen as the purge gas, what would be the oxygen concentration at which you would say (IN YOUR WRITTEN SOP) that work with a pyrophor can begin.

It would be really helpful to have this answer documented with data; ideally peer-reviewed, but hard anecdotal - not just opinion - would be ok.

And, I really do not care about t-BuLi, but used it as an example. Again, I am trying to find support for pyrophor use which is analogous to hydrogen, where the data clearly support <5% being not ignitable no matter the hydrogen concentration.

Thank you for continuing this discussion


From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**] On Behalf Of Melissa Charlton-Smith
Sent: Friday, September 25, 2015 6:45 AM
Subject: Re: [DCHAS-L] Pyrophorics

Neal, are you speaking the common 1.5% to 1.7% solution in pentane? The LEL of pentane is 1.5% (10% LEL, 1,500 ppm) which doesn't really answer your question about t-BuLi itself. Like you I have searched and the best I could fine was how to isolate t-BuLi solutions to pure crystalline form, but it was never exposed to varying % of oxygen, all was done under argon and/or nitrogen.


From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**] On Behalf Of NEAL LANGERMAN
Sent: Thursday, September 24, 2015 4:15 PM
Subject: [DCHAS-L] Pyrophorics

Does anyone have any citations for the low limiting oxygen concentration of pyrophoric compounds. I am specifically looking for the oxygen percentage at which compounds such as t-BuLi become non-ignitable. For example, that value is 5% for hydrogen. I have found a reference for silane, but, as is typical for silane, there are a myriad of confounding issues.

I have searched both SciFinder and Science Direct and have not found helpful data.




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