# What metal are these lab crucibles made of? **URL:** \ **Category:** Factual Questions\ **Created:** [June 8, 2012, 11:08am UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484 "2012-06-08T11:08:10Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [June 8, 2012, 11:08am UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/1 "2012-06-08T11:08:10Z")
There are a few metal crucibles in the lab whose origin and use nobody knows of. They are perhaps 50 by 50 mm or so, and a couple mm thick. They feel denser than steel to me, but ring about like steel to the touch. They have a dull dark gray color with hints of varying mild hues of blue and purple and brown. I wonder what they’re made of. Any way these could be platinum? Does platinum get an oxide layer look like these have? Are they more likely tantalum? Something else? Any real easy way to tell? I doubt it’s worth submitting samples for analysis. Thanks! ---
**Author:** ![Panurge](https://avatars.discourse-cdn.com/v4/letter/p/fbc32d/32.png) [@Panurge](https://boards.straightdope.com/u/Panurge)\ **Post date:** [June 8, 2012, 11:11am UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/2 "2012-06-08T11:11:33Z")
> [@Napier](#): > > There are a few metal crucibles in the lab whose origin and use nobody knows of. They are perhaps 50 by 50 mm or so, and a couple mm thick. They feel denser than steel to me, but ring about like steel to the touch. They have a dull dark gray color with hints of varying mild hues of blue and purple and brown. > > I wonder what they’re made of. Any way these could be platinum? Does platinum get an oxide layer look like these have? Are they more likely tantalum? Something else? Any real easy way to tell? I doubt it’s worth submitting samples for analysis. > > Thanks! Could you take a picture of them? And perhaps calculate the density of the material (by water displacement, for instance)? ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [June 8, 2012, 12:59pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/3 "2012-06-08T12:59:18Z")
I’m going to gues zirconium. Platinum is too expensive for crucibles that large. [Fisher carries them](http://www.fishersci.com/ecomm/servlet/fsproductdetail_10652_793575_29104_-1_0). ---
**Author:** ![IntelliQ](https://avatars.discourse-cdn.com/v4/letter/i/e99b99/32.png) [@IntelliQ](https://boards.straightdope.com/u/IntelliQ)\ **Post date:** [June 8, 2012, 1:21pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/4 "2012-06-08T13:21:46Z")
> [@Panurge](#): > > Could you take a picture of them? And perhaps calculate the density of the material (by water displacement, for instance)? You cant identify the type of metal by how much water it displaces. (For example a sheet of low carbon sheet steel will displace the same amount of water or space as a sheet of aluminum, yet both have different densities which account for the weight difference between steel and aluminum. The density of steel is .2833 off the top of my head. Can’t remember any of the aluminum alloys off hand) ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 8, 2012, 1:25pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/5 "2012-06-08T13:25:08Z")
> [@IntelliQ](#): > > You cant identify the type of metal by how much water it displaces. I think it was implied in **Panurge** ’s post that you would also weigh them, as well as measuring their volume. ---
**Author:** ![campp](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@campp](https://boards.straightdope.com/u/campp)\ **Post date:** [June 8, 2012, 1:48pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/6 "2012-06-08T13:48:57Z")
Titanium? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 8, 2012, 1:53pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/7 "2012-06-08T13:53:07Z")
Titanium would not feel denser than steel. Tungsten would. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [June 8, 2012, 1:54pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/8 "2012-06-08T13:54:49Z")
Platinum crucibles can get that big. I’ve worked with them. But they’re absurdly expensive, so they tend to only be used in special circumstances where you don’t want interactions between the crucible and the contents, as when you’re making sample batches of glass. (After you’re done, you dunk the crucibles in hydrofluoric acid to dissolve the glass off). Unless you were involved in a specialized activity like that, I suspect they’re not platinum. The quick, undergrad solution to this is to measure the density - weigh the crucibles, then find their volume by putting it into a graduated container and seeing how much water it displaces, then divide weight by volume and compare against the known densities of varioous metals and alloys. There’s more uncertainty to this that you’d think, but platinum, at 21.45 g/cm[sup]3[/sup], is pretty dense, and would be easier to identify. ---
**Author:** ![Si\_Amigo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/si_amigo/32/2877_2.png) [@Si\_Amigo](https://boards.straightdope.com/u/Si_Amigo)\ **Post date:** [June 8, 2012, 1:58pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/9 "2012-06-08T13:58:59Z")
Sounds like [graphite](http://www.bjgreatwall.cn/p31.aspx) to me. ---
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [June 8, 2012, 2:27pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/10 "2012-06-08T14:27:28Z")
I was going to suggest contacting Arthur Miller, but I see he died in 2005. ☹ ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [June 8, 2012, 3:13pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/11 "2012-06-08T15:13:27Z")
I’ve seen lab equipment like that made of lead. (This would have been made back in the old days, but then again, who throws out lab equipment?) Of course lead would be heavy and scratch easily. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 8, 2012, 3:14pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/12 "2012-06-08T15:14:31Z")
> [@kunilou](#): > > I’ve seen lab equipment like that made of lead. (This would have been made back in the old days, but then again, who throws out lab equipment?) Of course lead would be heavy and scratch easily. Lead would not ring when struck. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [June 8, 2012, 4:22pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/13 "2012-06-08T16:22:06Z")
> [@kunilou](#): > > I’ve seen lab equipment like that made of lead. (This would have been made back in the old days, but then again, who throws out lab equipment?) Of course lead would be heavy and scratch easily. A crucible is a container for melting things (especially metals) with high melting points, right? I think lead would be a particularly bad material for that application. The softness of lead would be an issue as well. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [June 8, 2012, 4:33pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/14 "2012-06-08T16:33:25Z")
Tungsten maybe? It is a good refractory metal, and quite dense and hard. ---
**Author:** ![randomface](https://avatars.discourse-cdn.com/v4/letter/r/5fc32e/32.png) [@randomface](https://boards.straightdope.com/u/randomface)\ **Post date:** [June 8, 2012, 4:36pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/15 "2012-06-08T16:36:54Z")
Can you scratch the material? Tungsten carbide is good to a pretty high temp (2870 C) and is pretty dense. Fairly brittle, but very hard. ---
**Author:** ![fumster](https://avatars.discourse-cdn.com/v4/letter/f/e9c0ed/32.png) [@fumster](https://boards.straightdope.com/u/fumster)\ **Post date:** [June 8, 2012, 4:38pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/16 "2012-06-08T16:38:54Z")
> [@Mangetout](#): > > I think it was implied in **Panurge** ’s post that you would also weigh them, as well as measuring their volume. Eureka ---
**Author:** ![Toucanna](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@Toucanna](https://boards.straightdope.com/u/Toucanna)\ **Post date:** [June 8, 2012, 5:02pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/17 "2012-06-08T17:02:22Z")
@ **kayaker** & **fumster** : Boo!!! Hiss!!! Philistines!!! 😃 ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [June 8, 2012, 5:11pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/18 "2012-06-08T17:11:08Z")
Why would anyone use pure platinum? Couldn’t one use platinum plated (or coated someway) steel for the same effect? I know coatings may suffer in high temperature ranges, but I’d expect some method to produce a suitable platinum surface at a fraction of the cost. ---
**Author:** ![Bill\_Door](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)\ **Post date:** [June 8, 2012, 5:34pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/19 "2012-06-08T17:34:29Z")
> [@WarmNPrickly](#): > > Why would anyone use pure platinum? Couldn’t one use platinum plated (or coated someway) steel for the same effect? I know coatings may suffer in high temperature ranges, but I’d expect some method to produce a suitable platinum surface at a fraction of the cost. The platinum is much more refractory than the steel. You can’t run sodium fusions in steel. I’m still voting for zirconium. It’s a good alternative to platinum, and much cheaper. It’s density is 6.52 g/cm3, slightly less than steel, but I don’t think the OP measured the density other than by hand, so close enough. They’ll ring like steel. You’d never forget what a platinum crucible that size was for, it costs thousands of dollars, maybe tens of thousands of dollars each. ---
**Author:** ![pravnik](https://avatars.discourse-cdn.com/v4/letter/p/8edcca/32.png) [@pravnik](https://boards.straightdope.com/u/pravnik)\ **Post date:** [June 8, 2012, 7:16pm UTC](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484/20 "2012-06-08T19:16:43Z")
Zirconium has a melting point of 3371 °F, while tungsten’s is 6192 °F. Just set your kitchen oven for around 4000 degrees, and if it melts, it was zirconium. [Next page](https://boards.straightdope.com/t/what-metal-are-these-lab-crucibles-made-of/624484.md?page=2)