White Yeti
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Where to get "impure" elemental selenium.
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.
"Ja, Kalzium, das ist alles!" -Otto Loewi
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Mercedesbenzene
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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
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Mixell
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http://www.ebay.com/sch/jarmondbrinkley/m.html?_nkw=&_ar...
Got pure and impure powder, the prices are quite good.
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White Yeti
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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.
"Ja, Kalzium, das ist alles!" -Otto Loewi
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Endimion17
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This is something I was dreaming of since childhood.
Weird dreams, I know. 
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Mr. Wizard
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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
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White Yeti
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Thanks to everyone for the info!
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IrC
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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]
"Science is the belief in the ignorance of the experts" Richard Feynman
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Endimion17
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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.
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Arthur Dent
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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
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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Mr. Wizard
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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%)
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IrC
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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.
"Science is the belief in the ignorance of the experts" Richard Feynman
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woelen
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I can confirm this. I purchased the pure form and it really is pure. It dissolves completely cleanly in nitric acid.
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