Sciencemadness Discussion Board - Metal Shot Heating Bath

Metal Shot Heating Bath

JJay - 27-1-2016 at 22:27

I have made a couple of attempts at creating a heating mantle and have so far been unsuccessful. So I was wondering what kind of metal shot might make a good heating bath. Copper has some attractive properties but is pretty expensive.... Would steel BBs make a good heating bath for use with mechanical stirring, or are they too large/not conductive enough? Also, what cheap and readily available shot might work well with magnetic stirring?

[Edited on 28-1-2016 by JJay]

DutchChemistryBox - 28-1-2016 at 02:51

http://www.labarmor.com/lab-armor-beads-for-lab-water-baths/

I use those, you can request a free sample. If you ask a friend to request a second sample then you have more then enough for home use.

[Edited on 28-1-2016 by DutchChemistryBox]

JJay - 28-1-2016 at 03:59

Quote: Originally posted by DutchChemistryBox

http://www.labarmor.com/lab-armor-beads-for-lab-water-baths/

I use those, you can request a free sample. If you ask a friend to request a second sample then you have more then enough for home use.

[Edited on 28-1-2016 by DutchChemistryBox]

"Starting at $1399" - I think I would definitely have to try a sample before making that purchase.

Their beads look quite a bit larger than BBs. So I guess BBs would probably work for thermal transfer, although they would tend to shift/roll around more than beads.

Sulaiman - 28-1-2016 at 05:30

Also note that those beads are rated for -80 to +180 celcius.

MrHomeScientist - 28-1-2016 at 05:31

Those are extremely expensive for just being aluminum shot. I'd like to try making some by pouring molten aluminum into water. Would be a hell of a lot cheaper, if you have a furnace. I built one out of an old charcoal chimney and hair dryer.

careysub - 28-1-2016 at 06:17

There have been a couple of threads on this recently, which I believe you read.

There are cheaper aluminum shot/pellet sources than LabArmor:
http://www.sciencemadness.org/talk/viewthread.php?tid=64259
http://www.sciencemadness.org/talk/viewthread.php?tid=64841

Look up the vendor "handi-ramp510" on eBay: 10 lb of aluminum for $50.

Aluminum conducts heat 5 times better than steel, and is 1/3 the weight.

There is also copper metal powder on eBay $52 for 4 lb (or $120 for 10 lb). Copper conducts twice as well as aluminum (but is also 3 times denser).

Prices:
Lab Armor beads: $100/Liter
handi-ramp510 pellets: $23/Liter
Copper powder: $178/Liter

I was just looking at a chem lab handbook about "metal baths" - molten low mp bismuth-lead alloys. The really low mp alloys all either have cadmium in them, which would make me wary of cadmium fumes, or indium which is really expensive.

Rose's metal with an mp of 98 C/208 F is the lowest mp alloy with neither cadmium or indium and is $340/Liter from Rotometals (its density is 9.7).

It occurs to me that combining the aluminum pellets with the copper powder might make a good substitute to using a liquid metal bath. The super-efficient conducting copper powder would fill the pellet void giving a boost to thermal conductivity in two ways.

Maximum random packing density for spheres is 64%. A mix of pellets and powder would be something like 60% aluminum pellets (assuming the squat cylinder pellets don't pack quite as tightly), 40% copper powder (copper powder is not solid, so it is something like 30% copper metal and 10% air).

This would make a dry bath costing $85/Liter, with a density of 4.3.

BTW - I don't think "shifting" is a problem with a bath. You would presumably clamp your flask in place, then pour in the bath beads.

[Edited on 28-1-2016 by careysub]

MrHomeScientist - 28-1-2016 at 07:07

A molten metal bath is an interesting idea. I've made some low-melting alloys (one liquid at room temperature, which I have a video on) so this would be cool to try. The problem, at least with alloys I've made, is that they usually wet glass. It seems like gallium is the culprit there, and possibly indium. So if your requirements allow you to use an alloy without these metals, it might not stick so much.

JJay - 28-1-2016 at 08:05

I've considered using zinc pennies, but I'm concerned that they might melt on the hotplate.

XeonTheMGPony - 28-1-2016 at 08:33

IMO being a one time investement with high resale value I'd just go with course copper my self (What I'll be doing personaly)

careysub - 28-1-2016 at 08:44

Quote: Originally posted by MrHomeScientist

A molten metal bath is an interesting idea. I've made some low-melting alloys (one liquid at room temperature, which I have a video on) so this would be cool to try. The problem, at least with alloys I've made, is that they usually wet glass. It seems like gallium is the culprit there, and possibly indium. So if your requirements allow you to use an alloy without these metals, it might not stick so much.

I forgot to mention, the lab manual prescribed coating the flask with graphite to prevent metal from adhering.

XeonTheMGPony - 28-1-2016 at 08:45

IMO being a one time investement with high resale value I'd just go with course copper my self (What I'll be doing personaly)

JJay - 28-1-2016 at 11:11

Copper pennies contain more than one cent worth of copper, but who has time to gather enough to fill a bath?

The Volatile Chemist - 28-1-2016 at 13:55

Quote: Originally posted by MrHomeScientist

One could always use a container other than glass. Of course the cheapest alternative would be metal. Do gallium alloys alloy with metals like iron/steel when hot?

chemrox - 28-1-2016 at 15:07

I would suggest using an electric lead melting pot with woods metal. Woods metal is a time honored mixture for heating glassware to high temperatures but be careful. I destroyed a heating mantle and warped a flask running an exothermic reaction. Check the thread on oil baths and consider sand.

JJay - 29-1-2016 at 13:20

Apparently there are still lots of copper pennies. I am told that coin collectors regularly buy $25 boxes of pennies from banks. A few hundred copper pennies weighs a kilogram.... It just might be worth sorting through enough pennies to make a copper bath.

Herr Haber - 30-1-2016 at 11:14

I once had this idea and went to my local armory to get some copper BB's.
If I remember correctly, they cold me they were only copper coated so they would eventually melt.

Instead, they suggested I go find an armory that sells non lead shot (steel) because of ecological reasons many people are fighting against the use of lead.
I never pursued the idea, using ultra fine and pure sand from a quarry I have nearby but I guess different sizes of bird shot would provide good thermal conductivity and be a lot easier to cleanup.

JJay - 30-1-2016 at 14:09

BBs are usually steel with a copper, zinc, or stainless coating.

JJay - 14-2-2016 at 05:59

I decided to go with copper pennies. I can get $20 worth/day from a local credit union, and about 20% are copper. This is around 300 ml of pennies at around 1200 grams from $20 worth of pennies. Sorting them takes time, so I do it while running distillations.

careysub - 14-2-2016 at 07:46

Quote: Originally posted by JJay

I decided to go with copper pennies. I can get $20 worth/day from a local credit union, and about 20% are copper. This is around 300 ml of pennies at around 1200 grams from $20 worth of pennies. Sorting them takes time, so I do it while running distillations.

How big a fraction of copper pennies are you finding?

1982 minted both zinc and copper, are you sorting these by weight (though a few zinc in the mix is not exactly a disaster). (There are also rare 1983 pennies accidentally minted in copper!)

If you are buying pennies for this purpose presorted copper pennies are available from eBay.

When I did this from a relative's coin hoard I use a 0.1 g scale to sort the 1982, but found the situation a little more ambiguous than you might think. The minimum weight of a copper cent (new) is 2.98 g The maximum weight of a zinc cent is 2.60 g, And I found an even wider variation from wear (on the one hand) and oxidation (and possible other deposits) driving the weight up. Dropping the coin on tile helped in some cases.

I found about 1/3 copper but I think the hoard may have selectively enriched in copper.

Not that this is of great import, but it should be noted that the thermal conductivity of the copper penny alloy (5% zinc, some tin) is only about 2/3 that of electrolytic/tough pitch copper (the nearly pure copper used in industry) .

[Edited on 14-2-2016 by careysub]

XeonTheMGPony - 14-2-2016 at 08:03

Seeing those pennies you'd be better off with the bb's

JJay - 14-2-2016 at 08:28

Quote: Originally posted by XeonTheMGPony

Seeing those pennies you'd be better off with the bb's

How so? The major problem with BBs is that they won't work with magnetic stirring.

I set aside the 1982 pennies and weighed them later. Zinc could cause problems at high temperatures, but it doesn't have to be a huge concern.

subsecret - 14-2-2016 at 22:02

How about copper turnings/filings? They're a little expensive, though.

Take solid copper wire, and cut it into segments The smaller the better.

http://www.ebay.com/itm/PURE-COPPER-FILINGS-6-LB-BULK-BOX-GR...

JJay - 14-2-2016 at 23:02

$10 per pound for copper is just outrageous.

I have seen penny sorting machines, but the ones that are ready to use out of the box aren't cheap.

I am still not exactly sure about zinc pennies that may have accidentally gotten mixed in.... Perhaps heating to 700 C and looking for molten blobs and destroying them with acid....

XeonTheMGPony - 15-2-2016 at 10:57

heat distrobution and contact area the penny's contact area seems hidious., if you could grind them then that would be better but as flat discs.....

JJay - 15-2-2016 at 13:06

I'll try some stress tests.

Funkerman23 - 15-2-2016 at 20:33

Quote: Originally posted by subsecret

How about copper turnings/filings? They're a little expensive, though.

Take solid copper wire, and cut it into segments The smaller the better.

http://www.ebay.com/itm/PURE-COPPER-FILINGS-6-LB-BULK-BOX-GR...

SOnner or later I need to find the formulas that's convert weight to approximate volume... This isn't the first time I've wondered about it but too many irons, not enough fire.

EDIT: JJay was right and I feel dumb.. Well better to be dumb for a moment and learn then carry on being an idiot. Thanks!

[Edited on 16-2-2016 by Funkerman23]

JJay - 15-2-2016 at 21:41

Quote: Originally posted by Funkerman23

Quote: Originally posted by subsecret

SOnner or later I need to find the formulas that's convert weight to approximate volume... This isn't the first time I've wondered about it but too many irons, not enough fire.

Huh? You use the specific gravity (density) of the material, which is specified in something like grams per cubic centimeter. You can also account for empty space by multiplying by (100% - empty space %). This is elementary school math.

[Edited on 16-2-2016 by JJay]

gsd - 16-2-2016 at 02:58

I am surprised that nobody has come up with "Woods Metal Heating alloy".

I came across it while searching for a patent on NaBH4 (US 2898184).

Wood's metal, also known as Lipowitz's alloy or by the commercial names Cerrobend, Bendalloy, Pewtalloy and MCP 158, is a eutectic, fusible alloy with a melting point of approximately 70 °C (158 °F). It is a eutectic alloy of 50% bismuth, 26.7% lead, 13.3% tin, and 10% cadmium by weight. The alloy is named for Barnabas Wood.

Given that this is a cocktail of "shunned" metals, I wonder will anybody here be inclined to "assemble" it.

https://en.wikipedia.org/wiki/Wood%27s_metal

gsd

XeonTheMGPony - 16-2-2016 at 03:35

I like my liver and kidneys too much to be bothered going any where near Cadnium in elimental form or its oxides.

careysub - 16-2-2016 at 04:11

Quote: Originally posted by Funkerman23

...
SOnner or later I need to find the formulas that's convert weight to approximate volume... This isn't the first time I've wondered about it but too many irons, not enough fire.

EDIT: JJay was right and I feel dumb.. Well better to be dumb for a moment and learn then carry on being an idiot. Thanks!

[Edited on 16-2-2016 by Funkerman23]

You could read this very thread where I do these calculations, giving both the input data and the result.

[Edited on 16-2-2016 by careysub]

careysub - 16-2-2016 at 04:43

Quote: Originally posted by JJay

$10 per pound for copper is just outrageous.

Over the last year the metal market price for copper has fluctuated between $2 and $3 a pound. This is a bulk market price.

If you buy copper (or any metal) in small quantities as a consumer that has been processed in some manner (like powdering, or shotting) you would normally expect to pay a few times the metal market price, or close to $10 a pound (at that price you can get shipping included). The cheapest source I know of for pure copper is Rotometals at $9/lb. This is a reasonable price for the pure metal.

Copper pennies, if you can acquire them at face value, are $1.46/lb, but aren't pure copper, they are an alloy that is 95% copper. But this is an historical anomaly and resulted in a special regulation being issued by the Treasury making melting bulk pennies down illegal to prevent them from being swept out of the circulating currency.

careysub - 16-2-2016 at 05:00

Quote: Originally posted by gsd

I am surprised that nobody has come up with "Woods Metal Heating alloy".

On this very thread I discuss Rose's metal, which has an mp of 98 C (vs 70 C for Wood's metal).

Two problems with Wood's metal:

1. Cadmium is a toxic, volatile metal. Cadmium's vapor pressure reaches 0.1% atm Pressure at 380C, it reaches 1% at 470 C.

2. Wood's metal costs $340/L (same as the much safer cadmium-free Rose's metal).

The 28C lower melting point for Wood's metal is not worth the toxic cadmium fumes.

For comparison (repeating the computations I made up-thread for convenience) the other metal baths discussed cost:
Aluminum pellets (from eBay seller handi-ramp510 ): $23/L
Lab Armor beads: $100/L
Copper powder: $178/L
Aluminum pellet and copper powder: $85/L

subsecret - 19-2-2016 at 21:01

What about cutting up fine steel wool? It would rust and wouldn't be compatible with magnetic stirring, but if you cut it finely enough, it would provide great heat transfer. Use 0000 grade.

JJay - 20-2-2016 at 00:06

They also sell copper scrubbing pads... they aren't as fine but I think they would work well too. That could get expensive, though.