# thermocouple question



## loco (Dec 15, 2007)

ok I know at least some thermocouples contain platinum but does anyone know if all of them do? and how much of it is really there? 

-Rich


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## Noxx (Dec 16, 2007)

No, only certain types but they are rare and for high temps applications.
Take a look on the wiki, you will get plenty of informations on the alloys of the thermocouples


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## loco (Dec 16, 2007)

ok anyone know what applications would typically have these rated for higher temps?


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## Irons (Dec 16, 2007)

loco said:


> ok I know at least some thermocouples contain platinum but does anyone know if all of them do? and how much of it is really there?
> 
> -Rich



A handy way to test to see if a thermocouple contains the Platinum group metals is to heat them in a reducing flame. They will glow brightly as they catalyze the oxidation of Carbon Monoxide to Carbon Dioxide on the surface and will remain bright after the flame is removed. The wire is also much heavier than other thermocouple wire alloys.

Pt/Pt/Rh thermocouple wire is very valuable, and all PGM.

I sold some a few years ago and wish now that I had held on to it.


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## Lou (Dec 17, 2007)

I know type S is Pt/Rh as I use one such thermocouple in the laboratory.
I think type R is also a Pt alloy, maybe with rhenium. All are high temperature, 1500C and above.

Most thermocouples in the lab are of high quality, so if you can get it on a college or university's giveaway, or a closeout from a private laboratory, you might well hit the jackpot, not just there but also in some of the nice platinum crucibles, foils, stir rods, and wire that they'll be bound to have. Look around in old or broken tube and muffle furnaces, remember, the higher the temp rating on the furnace, the higher the probability of you finding some PGM wire in there. If there's quartzware in the laboratory, that's usually indicative of Pt being there as well, most often they go hand in hand. On some really old (we're talking 1880s--1920s) furnaces, the filaments will be thick platinum wire!

Irons gave an excellent, non-destructive test.


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## lazersteve (Dec 17, 2007)

I posted a link quite some time ago with the answer here:

Thermocouple Types

I had the same question that was asked here, until I found the document linked to in the above in the post.

Steve


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## Irons (Dec 17, 2007)

If you can find a bit of Pt/Rh thermocouple wire, it's a good way to learn how to deal with Rhodium. Native Platinum usualy contains a couple of percent Rh, so learning the extraction with a known pure alloy is a good way to start and the ratios are similar.

Be prepared to shell out some big bucks, though.


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## jimdoc (Dec 26, 2007)

Here is a link on Rhenium;
http://www.resourceinvestor.com/pebble.asp?relid=38957

Looks like it should hold a spot up there with the PGM's.

Jim


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## goldsilverpro (Dec 26, 2007)

I used to handle a lot of scrap Pt-T/C wire. If you can figure a way to sort it into 2 separate Pt and Pt/Rh lots, and guarantee it, you could probably get more money selling it. Maybe something like density measurements, electronic probes, touchstone, etc., etc. Most Pt T/C wire that I've seen, has one wire of pure Pt and one of 90/10, Pt/Rh. There is, however, a little 5% Rh wire out there. A simple test for % Rh would be nice - accurate density measurements would work, but you'd need a few standards to calibrate it.


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## jimdoc (Dec 26, 2007)

It looks like the + wire in the R and S thermocouples will be
the wires with the rhodium R=13%rhodium and s=10% rhodium.
And B thermocouples will have 30%rhodium in the + wire and 
6% in the negative wire. 

So if you are the one dissasembling them you can keep them
organized and or know which ones to test for rhodium.

The rhenium thermocouples can be seen on this Omega link;
http://www.omega.com/techref/thermcolorcodes.html


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## goldsilverpro (Dec 26, 2007)

I used to buy bundles of mixed wires. I've also thought about first using a known pure Pt wire and measuring or zeroing the voltage made with a Pt/Pt couple. Any certain deviation with an unknown coupled with the Pt would be Pt/Rh. Go/NoGo.


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## Lou (Dec 27, 2007)

That should be pretty darn easy to do actually. Thermocouples work on potential anyways, so all you need GSP is to have a standard type S, R, B and then compare all of your used ones.


I'm actually in the market for a length of PtRh alloy wire, I'm building myself a tube furnace for at home use, and I need some for a thermcouple I'm making. I'm set on Pt wire, but I need some PtRh wire, anyone got any?


Little side story...
As far as rhenium goes, I just processed about 100g of it last week. It is a very interesting metal to deal with and presents unique challenges. It is very dense, very hard, corrosion resistant (depends on surface area), and relatively expensive. 

Back in 1928, Rhenium was $10,000 for a gram! It was one of the last elements to be isolated. Heck, I wish I had that 100g of rhenium back in 1928, I'd be a rich man! Too bad I can't time travel 

Curious thing about the rhenium I made was the fact that it was quite pyrophoric when it came out of the reduction furnace. Pyrophoric means it lights up when it hits air, burning to its oxide and the oxide of rhenium is volatile (mixed oxides are black, blue, brown). So when I went to transfer it out of the furnace and into the dish for mass, the rhenium caught on fire, right in my face! Very scary. Obviously I collected all of the burned material (about 4g) and kept it separate from the bulk lot, which I heated up with more hydrogen to make sure it was a good product.

Just goes to show, chemical inertness depends a lot on surface area. The powder I made was pretty fine, and very metallic looking. 


Lou


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## Noxx (Dec 27, 2007)

Hello Lou,
Could you tell me more about your tube furnace ? I know this will be really hot in there and I would like to know what type of insulation you are using.
I'm trying to make my own «ITC-100» but I still don't know it's composition. I'm looking for the lowest thermal conductible material (but still easy to get...)

Do you think sodium silicate mixed with finely ground perlite would work ?


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## Lou (Dec 27, 2007)

Gladly Noxx,


Our good friend Stefan, aka garage chemist at sciencemadness/versuchschemie has recently built a tube furnace for rather cheap.

Here is the link, it got me thinking. I use tube furnaces all the time, and the ones I work with are really expensive, more than I can justify spending. So I want to build my own 30"/75 cm one.



Sciencemadness Discussion Board - Homebuilt 1300°C tube furnace - Powered by XMB 1.9.11




I am using about 3" kaowool, .5" of alumina fiber ($$$$$), then a mullite tube (also a bit expensive). Then using kanthal A1 elements, a PID, and I have to make a thermocouple. I've bought all but the Pt/Rh, the elements, and the tube.


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## aflacglobal (Dec 27, 2007)

Translated version :arrow: http://tinyurl.com/2sjj3m


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## aflacglobal (Dec 27, 2007)

Check this out. :arrow: http://tinyurl.com/2zm33d


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## Noxx (Dec 27, 2007)

Looks very much like mine but a little bit cleaner :lol: 
But I will use kaowool as an external insulator.


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## lazersteve (Dec 27, 2007)

I wonder what it looks like *after* the first use?

Steve


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## loco (Jan 1, 2008)

Lou said:


> Gladly Noxx,
> 
> 
> Our good friend Stefan, aka garage chemist at sciencemadness/versuchschemie has recently built a tube furnace for rather cheap.



LOL garage chemist... we have a few of them in my area. dang folks keep blowing stuff up. 

sorry no disrespect intended to stefan aka garage chemist just sounded funny as that is what they are calling local meth makers (back yard chemists, garage chemist, basement chemist, etc... heck found out from a DEA officer in Louisiana while I was down there that my county here in Michigan is popular ... they even have thier own recognized production method called the st. joe county 1 bag method. on a more serious note sad thing is so many times here locally it is happening around kids and schools.)


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## Lou (Jan 1, 2008)

Yes, that damned methamphetamine is the scourge of the earth and it gives many people who have legitimate interest in amateur chemistry (as a hobby) a bad name. It really pisses me off. We may not be doing anything wrong, but all it takes is one officer of the law (albeit with good intentions) who does not know the difference between gold refining and clandestine drug synthesis to make you have a very bad year. It's happened before, it'll happen again. That sciencemadness forum has plenty of references about amateur scientists that have been falsely accused. Still, I'll warrant that for every false accusation, there's ten people that deserve prison...

Please remember that just because someone is doing chemistry in their garage, basement, or out in the shed, does not make them into some type of drug cook.


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## loco (Jan 1, 2008)

I know. believe me I know. I had a couple nice go arounds already. when I first went off looking for sodium nitrate I actually was asked if I was making meth with it, stunned I did some research. it appears nitrates in meth make a crappy over all product compared to what they desire. and when I bought sulfuric acid and murautic acid and had them sitting in the bed of the truck I was asked what I was useing them for. and because of the "bad chemist" we have in the area they threatened to turn me in to the police. I laughed and said great then they can learn how an electrolytic gold deplating cell works. Heck I'll give a class and see if someone can video tape it based off steve's videos. I'm sure everyone here would love that. LOL. I can see if now. 3-6 cops all sitting in my fathers garage/shed watching my best attempt at demo'ing steve's clips. wouldn't that be a sight? 

oh and I appologize for hi-jacking this thread and getting a little off track.


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## goldsilverpro (Jan 2, 2008)

In Texas, all sorts of meth related lab apparatus and chemicals were on the list. You couldn't even buy 500 mL erlenmeyer flasks without a gov. lab license. Once a year, you had to send them an inventory and you never knew when they would pop in.


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## Noxx (Jan 2, 2008)

That's probably why I can't buy any Sodium Nitrate nor Urea...

That's weird because I can still buy 25 kilos bag on eBay...


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