Mercury metal price experiences? / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

Mercury metal price experiences?

previous 1 2 3 4 next

Move Thread

LAN_403

Dr. Slack

Sat Oct 31 2015, 10:52PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

klugesmith wrote ...

Also looked into today's prices on the street. Some sellers on ebay have been getting $150/lb for triple distilled Hg in factory-labeled bottles!

Slightly less than one pound of the stuff (to stay within small quantities for shipping) delivered for $97

though not certain how triple distilled compares to 99.9995%

Sulaiman

Sun Nov 01 2015, 06:15AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

klugesmith,
to get a near accurate measurement of the electrical resistivity of your mercury using the capillary tube
measure its length,
then by measuring the volume of liquid (water or mercury) that it holds, measure its internal volume
and use (cross-sectional area) = volume / length
do not rely on manufacturers specification of internal diameter.
Also, use iron for connections as copper can (slowly) amalgamate with mercury.

P.S. I paid Â£35 for 1 kg of 'triple distilled' mercury, collect in person, a couple of months ago via eBay UK
for a mercury barometer that I am making using 9mm i.d. x 16 mm o.d. borosilicate glass tube.

Bored Chemist

Sun Nov 01 2015, 10:59AM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Just how badly impure would the mercury need to be before it made any difference?
All it needs to be is involatile, runny and dense.
Practically no metal is going to have a higher vapour pressure than mercury (OK to be honest, I'd need to check for Rubidium on a warm day- but how likely is that?)
If you can pour the stuff into the McCleod gauge then it's liquid enough.
So the only question is the density.
Well, the error in measurement will be proportional to the error in the density.
The gauge I have will just about show a 5% change in pressure, so if the density is within 1% the impurities won't matter.
You can check that reasonably easily by weighing a bottle full of the stuff WRT water.

klugesmith

Sun Nov 01 2015, 02:56PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Sulaiman & BC, I know the glass tube ID is loosely specified. Can get the actual average area by weighing the mercury it holds. Nominally 86 microliters, 1.16 grams. As the standard ohmists of 100 years ago discussed, the next challenge is the _uniformity_ of tube ID.

My goal is not accurate absolute resistivity, but accurate comparison of samples within, say, 0.1%. (Tempco is 0.09% per K). Would expect that dissolved metals, even silver or copper, increase the resistivity. I've been unable to confirm that, much less find coefficients, on the internet.

For McLeod gauges & thermometers, fluidity is not sufficient. We want a nice large contact angle (non-wetting) on clean glass. I have read that metallic contamination can spoil that. Droplets rolling in a dish can even develop "tails". Perhaps good behavior in a 0.6-mm capillary, and when rolling in dishes, indicates sufficient purity for McLeod gauges.

Here's a picture of Hg and eletrolyte in a 0.3-mm coulometric hourmeter tube, from 4hv discussion in 2009.

This person's beautiful photomicrographs appear to confirm that the solubility of gold in mercury is very limited.

Bored Chemist

Sun Nov 01 2015, 06:45PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Gold dissolves rather well in mercury. It's the basis of a technique for gold extraction.

Since you persist in your desire to measure the conductivity of a long thin tube full of mercury I may as well let you know how to check the uniformity of the cross section.
You put a small drop of mercury in the end of tube- just large enough to form a short slug of metal in the bore of the tube, and you measure the length. Then you blow it gently a little further down the tube and measure the length again and so on.
If the length of the mercury column is constant, the cross sectional area of the tube must also be constant.

Incidentally, does a solution of, for example, copper or silver in mercury conduct better or worse than pure metal?

Sulaiman

Sun Nov 01 2015, 08:50PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

judging by looking down my 9mm i.d. x 1.5m long borosilicate tubes,
and knowing that modern glass tubes are of continuous machine made uniformity
I expect uniformity of cross-sectional area to be much better than 'original' hand-pulled batches,
even though the specifications allow for relatively wide tolerances.

Bored Chemist
good tip, thanks

Bored Chemist

Wed Nov 04 2015, 10:03PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

The big problem is likely to be stuff like copper which dissolves but oxidises slowly to form a scum that then messes up the surface of the glass and stops the meniscus moving evenly.

One approach would be to blow air through the mercury for a while (venting the vapour laden air to a trap of some sort. I think iodine on charcoal is traditional) and then clean it by the "filtering" method I described earlier.
(Ozonised air might work even better)

Sulaiman

Thu Nov 05 2015, 05:33AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

For my barometer I cleaned the inside of the glass tubing, and the mercury, with a dilute nitric acid soak.

Bored Chemist

Thu Nov 05 2015, 08:55PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

That's fine, but in the case of the Hg, it depends on the impurities diffusing to the surface where they can get removed by the acid.

klugesmith

Sun Nov 08 2015, 06:01PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

On these disparate topics...

One ebay seller has recently sold 3 lots, each 0.98 pounds of mercury for $89 incl. shipping. Listed as 99.999%, "cleaned to ACS Reagent quality". Bidding stands at $26 for a lot of 325 grams from another seller.
[edit] This U S Geological Survey report gives the price in 2014 as $1850 per flask ($24 per lb, $54000 per metric ton).

Guidechem shows industrial suppliers today offering multiple-flask quantities at US $30 to $48 per kg.
Here's a super-flask for transporting up to 1 metric ton of mercury:

After hours of online research into purification of mercury, it appears that most methods were covered in scholarly papers published more than 100 years ago. Hg was a necessity in many labs back then. Bethlehem Apparatus Company advertising called mercury "the purest metal" because its low MP and BP temperatures facilitated purification. Process steps can be categorized as:

Mechanical filtering (e.g. through chamois, or wad of cotton in a syringe, or pinhole(s) at the apex of a filter paper cone)

Enhanced air exposure (e.g. with bubbler, or specialized mercury "blender" called an oxifier) to oxidize base metals

Wet washing with alkali, dilute HNO3, etc. (e.g by shaking, or dropping fine spray through tall column of acid) to remove grease, base metals, etc.

Distillation, often under vacuum. Hulett showed around 1905 that dissolved zinc tended to come over in readily measurable concentrations. His oft-cited remedy is to bubble air through the boiling Hg and let it stream with the vapor into the condenser, at a pressure around 15 torr.

Electrolytic processing. Looks like this was the least common, but included by some researchers needing Hg for standard voltage reference cells.

So far with my 800 grams I have done shaking with dishwasher detergent, water, vinegar, and dilute HCl. Also pinholing. Wash fluids got dirty-looking and Hg looks much cleaner now.

That shaker bottle is exceptionally thick & heavy (about 40 grams without cap), and the corrugations help to break up the mercury when shaken while horizontal. As reported by others 100 years ago, shaking with vinegar left the mercury in mm-size balls ("like fish eggs") that took a long time to coalesce. Well illustrated in this thread on an alchemy forum:

[edit] All work was done outdoors over a wide plastic concrete-mixing tub. Shaker bottle cap was secured by hand during all shaking.
Sulaiman, how's your barometer working out? Got pictures?
For electrical resistance experiment (in 12" long horizontal tube), temperature control is critical. Any thoughts about practical ice baths, or sensor-controlled heaters, for uniformity & repeatability within 0.1 K?

previous 1 2 3 4 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob