National Shutdowns have put the lid on most shows.
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Fri Sep 25, 2020 6:50 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 15 posts ] 
Author Message
 Post subject: Table Spectrometer
PostPosted: Sun Jun 03, 2007 1:10 am 
Offline
Valued Contributor
User avatar

Joined: Sat Jun 02, 2007 8:03 pm
Posts: 179
Location: N. Idaho
Does anyone have any experience using a table spectrometer/goniometer such as the one made by Kruss? Accurate R.I measurements of unlimited range as well as measurements of dispersion are said to be possible but specimen size seems to be a limitation.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun Jun 03, 2007 5:40 am 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2658
The table spectrometer is useful if you 1) Get large specimens which you can polish flats on. 2) Are very patient and painstaking and maybe even a glutton for punishment.

It is true that if you can get a D line reading then by changing the color of the light and with no more trouble than the D reading was, you should be able to obtain readings using the B and G line or any other color you care to use. You would need to get some interference filters or spectral sources of the appropriate color.

I have a table spectrometer (An American Optical made in the 1950s) I have demonstrated its use to myself. Even with prisms and gratings it is not an easy instrument to use. I cannot imagine anyone using it for routine gemology. The Kruess instrument is or at least used to be sort of a hybrid between a table spectrometer and a Bunsen Table Spectroscope.

By the addition of some polarizers you could do Brewster angle measurements which would probably be easier than "angle of minimum deviation" measurements You only need one flat surface for that technique.

Check out the Hanneman-Hodgkinson Refractometer which actually works on similar principles.


Top
 Profile  
Reply with quote  
 Post subject: Table Spectrometer
PostPosted: Sun Jun 03, 2007 12:31 pm 
Offline
Valued Contributor
User avatar

Joined: Sat Jun 02, 2007 8:03 pm
Posts: 179
Location: N. Idaho
Thanks for the response.

I'm interested in determining highly accurate RI and dispersion values for correlation with some quantitative chemical analysis of unusual gems I've done with an electron microprobe. I've read that a good table spectrometer with a specimen prepared such that the angle between the faces does not exceed twice the critical angle, can be very accurate to beyond three decimal places. A couple of the species I am working with have R.I.'s that are above the limits of conventional refractometers.

In the early 80s I had a Kreuss high RI refractometer with a heated hemicylinder and some ultra-toxic Thallium based RI paste which might have worked but probably was not accurate enough. They no longer make the unit.

The Brewster angle refractometer is only accurate to about .01 so it wouldn't work for my application. Do you know who sells the Hanneman unit?

It looks like I may have to become a glutton for punishment afterall.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun Jun 03, 2007 3:12 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2658
Kruess has a nice website here:
http://www.kruess.com/downloads+M52087573ab0.html

The table spectrometers of which they only show two are in the spectrometer catalog at the bottom.

Since you are in the US you might look here:
http://www.surplusshed.com/pages/item/i1476d.html

I could sell you mine or loan it to you.
Send me a PM
Gene

PS
Quote:
In the early 80s I had a Kreuss high RI refractometer with a heated hemicylinder and some ultra-toxic Thallium based RI paste which might have worked but probably was not accurate enough. They no longer make the unit.


Aaah , the mighty Riplus!! I would love to get my hands on one of those. Did you own it?? You DO have to be careful with thallium. It isnt on my forbidden list but if I was handling it even I would be extra careful.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun Jun 03, 2007 5:56 pm 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1470
I have a Kruess 1836 spectrometer / goniometer, and it is a fine instrument. But as with any table spectrometer, it is a lot of work to properly align it.

It has a gaussian eyepiece, which means you don't have to use the method of finding the angle of minimum deviation to align it. I don't think Gene's old AO spectrometer has the Gaussian eyepiece... my old AO spectrometer doesn't. But even the simplest measurement with a diffraction grating (collecting atomic emission spectra) still requires about 20 alignment steps. And my students always bung it up the first time, so it is part of their learning experience to find out from their first measurements that it wasn't properly aligned.

I like to use the table spectrometer to measure the dispersion of prisms, so I am indeed a glutton for punishment.

The standard for table spectrometers, as I've heard, was the Gaertner-Peck, which is no longer made. But they show up on ebay every so often. This spectrometer has the Gaussian eyepiece.

The Surplus Shed spectrometer that Gene mentions is, I'm pretty sure, made in India.

The Kruess is basically the Mercedes of these table spectrometers (but I've heard that it still doesn't reach the level of the Gaertner-Peck). If you want a good Ford version, do all the same things at half the price, just not quite the same fit and finish, you could buy a PASCO spectrometer:
http://store.pasco.com/pascostore/showd ... 6&Detail=1


Another possibility is this one:
https://www.3bscientific.com/shop/u.s.a ... _1701.html

I don't know who the manufacturer is, but this spectrometer costs about the same as the Kruess while providing an angular resolution of 30 seconds (instead of the minute resolution of the Kruess and Pasco).

And if you have an unlimited budget and want the be-all, end-all table spectrometer, I'd suggest a Moeller-Wedel goniometer II:
http://www.moeller-wedel-optical.com/Go ... Gonio2.htm

The angular resolution of the Moeller Wedel is a mind-blowing 0.6 seconds!!!!


Top
 Profile  
Reply with quote  
 Post subject: Table Spectrometer
PostPosted: Sun Jun 03, 2007 6:16 pm 
Offline
Valued Contributor
User avatar

Joined: Sat Jun 02, 2007 8:03 pm
Posts: 179
Location: N. Idaho
Thanks very much for the info.

The Moeller Wedel is pretty impressive. R.I readings to five decimals? That could precipitate more questions than answers.

I appreciate the time both of you took to help. If you don't mind I may have a few questions as I'm fumbling around trying to figure things out initially.

Bruce


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun Jun 03, 2007 8:03 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2658
If you look at the Pasco unit , it is identical to the SurplusShed unit, both made in India. In India they still manufacture all the stuff that was in the Cenco catalog and Sargent Welch catalog when I was growing up and the Griffin and George catalog in England which I never saw over here.

Moeller-Wedel makes some surgical microscopes which are even more expensive than Wild-Leica and Zeiss. Definitely Benzer klasse. I have a MW hand spectroscope in my little collection which has a 13 degree dispersion, more than the Kruess or Zeiss.

If you would like some detailed consultation on table spectrometry go to this site: http://ioannis.virtualcomposer2000.com/spectroscope/
I am sure Ioannis would love to help you work the bugs out. Take a look at HIS table spectrometer which he built. It is a double prism unit. I think he bought his dispersion prisms from MW.

The Gemmary has been trying to unload this instrument for $2500 for years. Maybe it would do the job for you:
http://www.gemmary.com/instcat/07/07-001.html
He also has this unit:
http://www.gemmary.com/instcat/07/07-014.html

If I see anything on fleabay I will shoot it to you.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun Jun 03, 2007 9:45 pm 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1470
Yep, the Moeller Wedel is unbelievable... I was thinking it was more Lamborghini class, or whatever your most-expensive production-vehicle class is these days.

And Gene, you know I want to see that 'scope. :smt088 Post us a pic, at least!

Brian


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun Jun 03, 2007 11:09 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2658
I was looking for a suitable green emoticon to put on the reply about the Kruess RI Plus refractometer. (CZ table, REAL sodium lamp, heated base to melt the nasssty contact "liquid" and you probably needed to correct the RI back to room temp)

Picture will follow schortly.

I am waiting for MoDo to tell us we both need to get lives. :roll:


Top
 Profile  
Reply with quote  
 Post subject: Table Spectrometer
PostPosted: Mon Jun 04, 2007 12:34 am 
Offline
Valued Contributor
User avatar

Joined: Sat Jun 02, 2007 8:03 pm
Posts: 179
Location: N. Idaho
Brian, I think the Bugatti Veyron or a McLaren are the highest end luxury sports cars of the day. The Moeller-Wedel woud appear to have a resolution 50 times greater than the competition (0.6 vs 30) which is pretty remarkable.

As far as the Kr├╝ss RI plus unit is concerned, Gene, it was 26 years ago since I bought it and 21 years ago since I've seen it last, so the novelty has worn off for me. The hemicylinder, if I recall correctly, was strontium titanate, and trust me, you REALLY needed the sodium light source.

Bruce


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon Jun 04, 2007 9:48 am 
Offline
Gemology Online Royal Princess

Joined: Mon Oct 17, 2005 10:56 am
Posts: 6461
Location: The frozen north prairie :-/
:smt045

_________________
IIJA Registered Gemologist
GIA Graduate Gemologist


Top
 Profile  
Reply with quote  
 Post subject: Re: Table Spectrometer
PostPosted: Mon Jun 04, 2007 10:28 am 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1470
ggfgadgemg wrote:
The Moeller-Wedel woud appear to have a resolution 50 times greater than the competition (0.6 vs 30) which is pretty remarkable.


Yes Bruce, that's the way I read it, 50 times better angular resolution. But the Moeller-Wedel has a digitally-mapped turntable, whereas the others have turntables with machined angle marks that are read against a Vernier scale. One can observe a similar increase is resolution when moving from Vernier calipers (whose measurements can be read to the nearest 0.1 mm) to digital calipers (whose measurements can be read to the nearest 0.01 mm).

From this comparison, the increase in angular resolution is not too surprising. But it is still much better than anything I've ever worked with.

and MoDo, don't let Gene start putting words in your mouth!


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Thu Jun 07, 2007 10:03 am 
Offline
Valued Contributor
User avatar

Joined: Mon Jan 29, 2007 5:16 am
Posts: 308
Location: Silom, Bangrak, Bangkok
"I'm interested in determining highly accurate RI and dispersion values for correlation with some quantitative chemical analysis of unusual gems I've done with an electron microprobe."

Yeah, me too.

:)

_________________
Keep away from people who try to belittle your ambitions. Small people always do that, but the really great make you feel that you, too, can become great. ~Mark Twain


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Thu Jun 07, 2007 10:10 am 
Offline
Platinum Member

Joined: Tue Nov 29, 2005 2:02 pm
Posts: 2647
Quote:
electron microprobe


That type of high tech vulgarity could get you banned here. :wink:


Top
 Profile  
Reply with quote  
 Post subject: Table Spectrometer
PostPosted: Wed Jul 25, 2007 7:18 pm 
Offline
Valued Contributor
User avatar

Joined: Sat Jun 02, 2007 8:03 pm
Posts: 179
Location: N. Idaho
I purchased a high quality table spectrometer on eBay for $150. It is in new condition and represents a real bargain. The Seller has one more available. If you are interested PM me and I'll provide the info.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 15 posts ] 

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock