Identifying a metal and silver

[bpost1958]

I have had some metal for years that I can't figure out what it is. It is of a crystline structure on the broken pieces. A propane torch will not melt it. One side, I'll call the top looks like lead after it has hardened in a met pot. The other sides have the crystaline structure to it. How do I identify what it is?

I also have a few pounds of pure silver contact points from high energy contactors in old x-ray machines. Does any body have a company they know can be trusted to sell them to?

[johnly]

I have a XRF analysis instrument that will do the trick.

John

[bpost1958]

I have a XRF analysis instrument that will do the trick.

John

What is that?
How does it work?

Do I need to send some to you for testing?

Thanks!
Bruce

[JIMinPHX]

The “silver” that they made those contacts out of probably has cadmium in it. Some contacts were made out of pure silver, but they usually added cadmium to increase the current capacity. Don’t smelt that stuff.

There are places that specialize in buying small quantities of precious metals. They do an assay on the bulked lot of what you brought them & then give you a buy quote that you can either accept or reject. The guys seem to be pretty fair. I can’t remember the names of any of those places right now though. I think that they can handle the cad mix as well as pure. They usually pay spot price or just a hair off of it. Spot price on silver right now is about $17.20/oz.

[Gandolf]

Hi Bpost 1958,

I can make a wild guess as to the XRF devise works, and maybe if need be, Johnly can correct any errors that I make. The only drawback is that my explanation, even if I'm completely correct (which is only a maybe), may only lead to more questions than you had before.

XRF stands for X-ray Fluorescence. The devise has a simple principle of operation, but as in everything, the devil is in the details. The principle is that when a chemical element is exposed to an X-ray beam, the element absorbs some of the photons of the X-ray beam, which causes transitions in the element. What happens is electrons change energy levels in the atom. These energy transitions are "quantized", and only certain very specific energy tranistions are possible. These changes are very high energy changes and involve energy level changes that take place with electrons that are in inner shells of the atom.

After being hit by the X-ry beam, and absorbing the energy of the X-ray photon, the atom will flouresce, or give off an energy photon that corresponds to the energy trasition of the electron in the higher energy level orbital back to it's energy level in its' ground state (its' most stable low energy state.) It can also flouresce in stages, or smaller step transitions, until the ground state is again reached.

The key here is that all of these transistions have very specific energy changes, and consequently the photons given off are at extremely specific wave lengths for each element, and these are unique to that element. Thus by determining the wavelengths of the photons which fluoresce from the sample, one can determine the identity of the element that it came from.

The amount of photons given off by the sample is proportional to the amount of the given element in the sample. Thus, from the XRF you can determine what elements are present in the sample, and how much of the element is in the sample. (XRF is described as semi-quantitative, so the accuracy of the "amount" of the element present in the sample is an approximate number rather than an extremely precise value.)

However, all that aside, I am thinking that the identity of the metal you have is that it is not a metal at all. From the physical properties you describe, ie: does not melt, but rather breaks off in a crystalline way, I suspect that it is actually a compound.

Certain metals can form compounds with elements like sulfur to give compounds that look like metal, and have a metallic sheen, but are not in fact metals. These compounds break like the crystals that they are, and they often do not melt, but instead decompose when heated to a very high temperature. If you could melt these materials, it would be at a VERY high temperature.

An example of this type of material is iron pyrite, which is composed of iron and sulfur. The material is crystalline, having a cubic type of form with crystals breaking off at right angles with flat faces. The material is often of a gold sheen, but I have seen some that looks silver. The common name of this material is "fools gold."

The XRF data will tell you how much of what element is in the sample. If it turns out to be iron and sulfur, then iron pyrite is a good guess.

Another method, which will tell you the specific material that the sample is made from is XRD, or X-ray diffraction. The X-ray diffraction pattern is specific to a given crystalline material.

Regards,

Gandolf

[floodgate]

Gandolf:

Good explanation, in layman's terms ("people-speak"); thanks!

Din't I see you in a movie somewhere?

Fg

[Gandolf]

Hi Floodgate,

Nope, I wasn't in a movie, but Gandalf was.

I had read the Hobit books several years ago and was looking for a name to use on the old virtual fly shop fly tying bulletin board. Spelling has never been my strength, and it had been a few years since reading the books anyway.

I do applied research chemistry projects at our plant, plant troubleshooting, etc., and one of the guys used to call what I do "Wizard Work." Thus, "Gandolf" appealed, not realizing that I should have gone with "Gandalf". It has been Gandolf ever since.

Regards,

Gandolf