There are a couple reasons why mercury may be preferred over oil in a
high vacuum/ high purity vacuum line. First, oil tends to have a higher
vapor pressure. It also can absorb gasses and other contaminants which
can then be released back into the system when least convenient. Then
there is the fact that it wets glass. Mercury has none of these issues.
For applications such as you describe mercury may well be irreplaceable.
Dave
On 14/10/16 7:55 AM, Chance, Brandon wrote:
> Rob,
>
> You hit the nail on the head it seems. While I am still trying to get a handle on the exact research and uses of mercury in these labs, we are not talking about standard Schlenk systems used in a chemistry hood with mercury bubblers. These are Earth and Geosciences labs that look at isotopes and all of their systems are high vacuum systems and in some areas I have seen glass reservoirs with quite a bit of mercury attached to these systems. Based on the links you provided, these look like Toepler pumps.
>
> I am working on gathering more information now. For any of you that deal with the typical research lab in a Geosciences department, it is my experience that these are labs doing amazing research, but the equipment is a throwback to bygone eras. The field itself doesn‰??t seem to be as well funded as it once was, any attempts to modernize is usually met with, what is in many cases a valid, funding argument.
>
>
> Regards,
>
> Brandon S. Chance, M.S., CCHO
> Associate Director of Environmental Health and Safety
> Office of Risk Management
> Southern Methodist University
> PO Box 750231 | Dallas, TX 75275-0231
> T) 214.768.2430 | M) 469-978-8664
> bchance**At_Symbol_Here**smu.edu
>
> "‰?| our job in safety is to make the task happen, SAFELY; not to interfere with the work‰?|‰?? Neal Langerman
>
>
>
> From: ACS Division of Chemical Health and Safety on behalf of ILPI Support
> Reply-To: ACS Division of Chemical Health and Safety
> Date: Friday, October 14, 2016 at 9:34 AM
> To: "DCHAS-L**At_Symbol_Here**PRINCETON.EDU"
> Subject: Re: [DCHAS-L] Protecting Vacuum Lines during renovations
>
> Tilak, that‰??s a great question. For some applications, yes. For others, no.
>
> For example, if their system uses an old-school manometer for measuring evolved gases, operating at a reduced (or above atmospheric) pressure, or for use with a gas bulb to add specific amounts of gas to a system, it would be a tough sell for some researchers. Moving to electronic gauges may not be practical in these cases given issues such as calibration for different gases, compatibility, pressure ranges etc. However, for *some* cases, yes, moving to an electronic gauge is indeed feasible and should be encouraged.
>
> Oil as a replacement in bubbler and manometers can work on a low vacuum or Schlenk system where your main interest is pressure relief - simply turning up the flow in the system can provide back flow protection equivalent to a traditional mercury bubbler. But for high vacuum lines like these, there is usually a need for one traditional manometer which you need to pull full vacuum on. A mercury manometer only needs to be about a meter high because at full vacuum the height of the column is approximately 760 mm. Replace the mercury with oil and you‰??d need an oil manometer approximately 14 times as tall; simply not doable. Electronic gauges are the only practical alternative (although as I mentioned above, may not be feasible).
>
> One area you‰??ll still find large amounts of mercury in these kinds of labs is diffusion pumps. While mercury diffusion pumps work fine, if money can be found to replace them with oil diffusion or turbo molecular pumps, then now is the time to get those labs to change over. There‰??s no reason (other than lack of funds) to still use them.
>
> One mercury-laden device you can‰??t replace is a Toepler pump, which uses a god-awful amount of mercury (a liter or so) to trap and measure evolved/consumed gases. They are very rare beasts these days and marvel of old-school technology. If you come across one of these make sure that the PI has set up an appropriate secondary containment system for them! Video of one here: https://www.youtube.com/watch?v=MK3Pp8N4268 and a terrific PowerPoint of how they work here: http://molan.wdfiles.com/local--files/toepler-pump/toepler.ppt The power of these things for a certain set of narrow applications is incredible - for example, let‰??s say you were studying the uptake or evolution of a mixture of H2 and CO. After making your measurement of the total amount of gas, you can cycle the system through a catalyst bed (‰??burn tube‰??) to convert the H2 to H2O, trap out the water, and then directly determine the amount of CO (and therefore, H2) in that mixture. Very powerful. Of c!
ourse, each of these measurements takes a couple hours because the cycle time of that pump is probably 30-60 seconds.
>
> Rob Toreki
>
> ======================================================
> Safety Emporium - Lab & Safety Supplies featuring brand names
> you know and trust. Visit us at http://www.SafetyEmporium.com<http://www.safetyemporium.com/>
> esales**At_Symbol_Here**safetyemporium.com or toll-free: (866) 326-5412
> Fax: (856) 553-6154, PO Box 1003, Blackwood, NJ 08012
>
>
>
>
> On Oct 14, 2016, at 9:45 AM, TILAK CHANDRA > wrote:
>
> Hi Brandon:
>
> Is it possible to replace the mercury with other safe alternatives, such as oil?
>
> Thank you.
>
> Tilak
>
> From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Chance, Brandon
> Sent: Wednesday, October 12, 2016 4:19 PM
> To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
> Subject: [DCHAS-L] Protecting Vacuum Lines during renovations
>
> DCHASers,
>
> We have a building wide lab renovation project starting up that involves ventilation upgrades and installation of sprinkler systems. A number of these labs have glass vacuum line systems that are 6-12ft long, some containing various mercury containing components. Due to the size and intricacy of the systems, there is a significant hazard involved with dismantling them and the labs would like to leave them in place and have them protected in some fashion.
>
> Does anyone have any recommendations to have them crated in place or whom would be the best type of company to reach out to? I wouldn‰??t trust a standard crating company with this project and we are currently reaching out to the local scientific gas blower that made the systems for his suggestions.
>
> Thoughts would be appreciated.
>
>
> Regards,
>
> Brandon S. Chance, M.S., CCHO
> Associate Director of Environmental Health and Safety
> Office of Risk Management
> Southern Methodist University
> PO Box 750231 | Dallas, TX 75275-0231
> T) 214.768.2430 | M) 469-978-8664
> bchance**At_Symbol_Here**smu.edu
>
> "‰?| our job in safety is to make the task happen, SAFELY; not to interfere with the work‰?|‰?? Neal Langerman
>
>
> --- This e-mail is from DCHAS-L, the e-mail list of the ACS Division of Chemical Health and Safety. For more information about the list, contact the Divisional secretary at secretary**At_Symbol_Here**dchas.org
> --- This e-mail is from DCHAS-L, the e-mail list of the ACS Division of Chemical Health and Safety. For more information about the list, contact the Divisional secretary at secretary**At_Symbol_Here**dchas.org
>
> --- This e-mail is from DCHAS-L, the e-mail list of the ACS Division of Chemical Health and Safety. For more information about the list, contact the Divisional secretary at secretary**At_Symbol_Here**dchas.org
>
> ---
> This e-mail is from DCHAS-L, the e-mail list of the ACS Division of Chemical Health and Safety.
> For more information about the list, contact the Divisional secretary at secretary**At_Symbol_Here**dchas.org
>---
This e-mail is from DCHAS-L, the e-mail list of the ACS Division of Chemical Health and Safety.
For more information about the list, contact the Divisional secretary at secretary**At_Symbol_Here**dchas.org
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