Sciencemadness Discussion Board

Where to get "impure" elemental selenium.

White Yeti - 16-10-2011 at 11:50

I've had a lot of trouble finding selenium on the internet and it seems like there are only two ways I can buy selenium, either as a "vitamin supplement" or as a highly purified and expensive powder from Alfa Aesar.

The problem with the first option is that the "supplement" is extremely expensive for the amount of selenium it contains. The pure powder from Alfa Aesar is expensive (5$/g), mainly because it's 99.5% pure.

I'd like to know if anyone knows where to get elemental selenium that is not too pure, and still somewhat usable for most purposes. I'd be more than happy with a sample as impure as 85%.

Price is such an issue because I am planning on using relatively large quantities and high purity is not required for my purposes.

Mercedesbenzene - 16-10-2011 at 12:03

not sure if you need a powder, but element sales has a cheaper price for selenium chunks
http://www.elementsales.com/pl_element.htm#se

Mixell - 16-10-2011 at 12:11

http://www.ebay.com/sch/jarmondbrinkley/m.html?_nkw=&_ar...

Got pure and impure powder, the prices are quite good.

White Yeti - 16-10-2011 at 12:12

That's interesting. I thought element sales would be more expensive, since the elements have to be no only pure, but they also have to look good. A powder would be so much more convenient, but I could also make do with a lump as well.

Endimion17 - 16-10-2011 at 12:15

This is something I was dreaming of since childhood.
Weird dreams, I know. :D

Mr. Wizard - 16-10-2011 at 16:16

The print drums on old Xerox copiers used to be Selenium. A Selenium allotrope changes resistance with light, which allowed the projection of an image on a drum which while kept dark, had an image projected on it. Where the light hit, the charge was dissipated. The toner was then dusted on the drum, and stuck to the dark portions. A laser printer does the same thing, using a laser to print the image on a drum. It is digitally controlled, instead of an analogue process. It may be that the used laser print cartridges contain a drum with a layer of selenium. If they use the same process, maybe they use the same material? I must admit I haven't taken a laser printer apart, but the old Xerox machines had a real big drum, with a lot of selenium on them.

Alfred Morgan showed how to make a selenium photocell in one of his books. "The Boy Electrician".
It starts on page 394. You get extra nerd credit if you knew about this book, and double credit if you already have a copy ;-)
http://rawfire.torche.com/~opcom/tbe/the_boy_electrician.pdf

White Yeti - 16-10-2011 at 16:35

Thanks to everyone for the info!

IrC - 16-10-2011 at 23:52

Quote: Originally posted by Mr. Wizard  
The print drums on old Xerox copiers used to be Selenium. A Selenium allotrope changes resistance with light, which allowed the projection of an image on a drum which while kept dark, had an image projected on it. Where the light hit, the charge was dissipated. The toner was then dusted on the drum, and stuck to the dark portions. A laser printer does the same thing, using a laser to print the image on a drum. It is digitally controlled, instead of an analogue process. It may be that the used laser print cartridges contain a drum with a layer of selenium. If they use the same process, maybe they use the same material? I must admit I haven't taken a laser printer apart, but the old Xerox machines had a real big drum, with a lot of selenium on them.

Alfred Morgan showed how to make a selenium photocell in one of his books. "The Boy Electrician".
It starts on page 394. You get extra nerd credit if you knew about this book, and double credit if you already have a copy ;-)http://rawfire.torche.com/~opcom/tbe/the_boy_electrician.pdf


Depends upon the year. Drums around 81 started being ever higher percentages of Te and less Se for the liquid toner and dry toner machines. Also expensive as they traded in the old drums for rebuilding. From the mid 70's to 1979 you can easily get pure Se plated on Al drums especially in the Savin 770 series copiers. Just an FYI. Really neat were the Royal dry toner CDS drums if you need Cadmium Sulfide also. There used to be a dozen sellers of Se and Te powder and chunks on fleabay not over 5 years ago but I see none of them selling in the US today.

If in the UK you could try here:

http://www.ebay.com/itm/SELENIUM-200g-Se-54-89-/370397673805...

I just realized I may be a nerd.


[Edited on 10-17-2011 by IrC]

Endimion17 - 17-10-2011 at 05:36

Although the procedure should work, I doubt those drums are a viable source. Even if there's pure selenium on them, it's vacuum deposited, therefore it should be a very thin layer of it, perhaps similar to the aluminium layer when you vacuum-deposit it on telescope mirrors.

Arthur Dent - 17-10-2011 at 06:55

I remember when I was a tech at Xerox many decades ago we used to work on high production imagers (a 15 ft-long laser printer) and these machines didn't use a drum, it was actually a large aluminium alloy belt about2.5 ft wide by 5 ft circumference, covered with selenium, and whenever we used to change one, the old one were sent to recycling.

There was quite a bit of Selenium on those because when you kinked one, the selenium layer would peel off and flake, similar to chrome plating on old car bumpers. I never thought of keeping one to salvage the Se. Anyway, for any belt changed, the used belts were swapped with new ones and were closely counted. Same thing with the awesome argon lasers when they were replaced in these machines. I would have loved to keep one of them.

Robert

Mr. Wizard - 17-10-2011 at 09:12

Well I see I'm seriously out of date on the toner drum technology. Selenium Sulfide is also available in OTC (1 %), and prescription (3%) anti dandruff shampoos , Selsun Blue. I doubt this would be a cost effective method of getting Selenium, but it might be an interesting project. It is also contained in other anti-fungal medicines such as Tersi Foam (2.25%)

IrC - 17-10-2011 at 11:20

The Se and or Te is easy to get off. The hard thing is it not coming off. A slight scratch does it and you can scrape it off the drum without much trouble. But a painstaking way to get tiny amounts of something only 16 bucks for 200 gm in one of the ebay auctions Mixell posted if you go check the list. In 1981 I worked for Savin Corporation in their research and development lab playing with toners and charge to mass ratios for the Landa process competing against Xerox trying to get that legal letterhead look in a copy.

woelen - 17-10-2011 at 14:07

Quote: Originally posted by Mixell  
http://www.ebay.com/sch/jarmondbrinkley/m.html?_nkw=&_ar...

Got pure and impure powder, the prices are quite good.

I can confirm this. I purchased the pure form and it really is pure. It dissolves completely cleanly in nitric acid.