  Selenium toner. 
Back in the dark ages photography involved soaking paper in a series of strange chemicals to make images appear on it.  This 22g/l solution of sodium selenide was apparently one of them.   
Source: eBay seller 20fec 
Contributor: Theodore Gray 
Acquired: 24 March, 2009 
Text Updated: 24 March, 2009 
Price: $15 
Size: 10" 
Purity: 1%
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