A Technical ?

Do chromophores(elemental, oxides, etc) ever show up in XRD analyses? Please be gentle, I'm not a hard scientist, and I cleave easily. LOL


PS. Is it just me, or do many enthusiasts of our ilk(Bill O'reilly would be proud) enjoy the music of Steve Hackett?

PPS. No, Gail. That's not the answer to a previous post. Think, verbous.


TTFN

I meant verbose. I must have been thinking in French. LOL


TTFN

Chromophores tend to be in the ppm-ppt ranges. XRD determines the major elemental arrangement of the crystals structure and really doesn't vary that much with compositional changes in that range.

Yes they can show up. In certain cases the chromophore is actually an elemental part (usually a transition element) of the mineral structure such as with copper in azurite. In the case of chromophore impurities it will depend on their concentration.

Dave, all chromophores are not impurities.

Albert,

Thanks, but you didn't have to be that gentle.

My conception of a chromophore, mineralogically speaking, is a colorant which is not a part of the molecular/primary chemical structure. Not knowing which of these are color-center caused(so please bare with me), but I was thinking on the order of tourmaline, spinel, quartz, corundum, beryl, and jeremyjevite(oooooooooh).

By the way, "copper" doesn't make azurite blue. I CAN JUST SEE THE MAIL ROLLING IN NOW. Jolyon, save me!!!!!!!!!!!!!


TTFN

Well, X-ray diffraction really doesn't tell you what elements you have, but is more dependent on their arrangement (as well as a certain amount on their atomic weight). You might be able to determine something is azurite, but XRD wouldn't tell you which element is the chromophore. You are usually better off studying the mineral with a spectrometer to determine the exact spectrum and what elements (etc.) might contribute to it.


[minerals.caltech.edu]

[www.minsocam.org]



Edited 1 time(s). Last edit at 05/01/2008 08:45PM by David Von Bargen.

Now!, this should get some mail going, but it won't be my fault.

It's a tad off the subject, but..................

A gentleman(PhD in chemistry) with whom I periodically worked for ,at the now defunct Engelhard Corp, would say that azurite is every color, BUT blue, etcetera, etcetera, etcetera.


TTFN

By the way, the Engelhard Corp. is NOT defunct.

The original question asked if XRD could determine a chromophore not if it could tell if it were a chromophore or not. The fact is if an atom such as copper is in the chemical structure (not an impurity) it will be detected by XRD. Steve, a chromophore is a color generating center it does not have to be a impurity but can be a part of the structure and yes copper is a chromophore in azurite also causes the green in malachite. It is true that azurite is blue because the wave lenghts of light that hit your eye are blue not the azurite. But I get the feeling you are only trying to go in circles here.

Peter,

OK. Bought, and dissected by BASF.

Show me something current (ie in the last year) labelled as an Enghard product, or service(Charles would probably appreciate having to stop rolling in his grave). They've been rebranded for more than a year. If I'm wrong, I owe you one, but you'll be hard pressed to prove it.


TTFN

PS Are you a NJ resident?

Steve, not to be technical but a chromophore is not necessarily a colorant, for example the transition element ions are themselves not colored but when placed in a crystal ligand field their electron levels are affected which cause light absorption and therefore color.

Albert,

This is what makes this website so much fun.

As I degress, to be more specific, if not in more technical error, but in my thinking a chromophore is a substance which causes the perception of color, directly, or in-directly.

Primarily, the sky is blue not because N2 is blue at STP, but because of the size of the N2 molecule, and how a particular part of the visible spectrum is scattered more effectively, i.e. Rayleigh Scattering.

Now, would everyone stop whining, and go have a pint/mug/long-neck/yard(liter).


TTFN

Yes "a chromophore is a substance (not really) which causes the perception of color, directly, or in-directly." But you mentioned before it was a "colorant" and that is what is in error. A colorant is by definition a dye or pigment. I don't meant to be technical but after being a color chemist for 30 years at Kodak, I tend to use the terms correctly.

Albert,

All right I'll say it...what color were/are you? LOL

Does this mean you were/are a SCATTERologicalist. Get it! LOL

BTW, now I'm even more confused as to the true definition of - chromophore. I'm sure J B has the answer.


TTFN

"The Physics and Chemistry of Color", 2nd edition by Kurt Nassau ISBN 0471391069. I think this is THE reference on color.

It took a New Jersey(ian/ite) to give a substantive answer.

PS Have you been to the Olde Mill Inn lately(I know it's the Grain House, now)?
Just a fond memory of the (ahem) sixties...

Still a beautiful spot as I remember it eight years ago.


TTFN

Hi Steve,

I haven't been there in quite some time, but am planning to take my wife there for Mother's Day in a couple of weeks.

Don

My head has stopped spinning.

Can we all agree that "a" definition of a chromophore is: a color generating center, which causes the sensation of color, whether through it's structure, composition, or other mechanism, either in whole or in part.

This will be my last word on the subject. I'll shut up now.

TTFN

No.

A chromophore (from greek "chroma" = colour, and "phoron" = carrier) is a structural unit that absorbs light in the visible or near-UV range (due to the line width of UV absorptions, the flank of a maximum in the near UV range will extend into the visible range, giving the respective compound a yellow colour). "Structural unit" is meant very generally. It can be part of the constituents making up the the respective compounds, or part of the impurities incorporated into them. Chemically, it can be anything: an ion, an atom, a molecule, or only a particular part of a larger molecule (organic chemists use the term "functional group".

Colour is considered as a permanent property of a compound, and not just seen when particular mechanisms are working (such as scattering). Therefore, the definition only includes absorption.