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Old Jun 1st 2017, 02:59 AM   #1
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Join Date: Jun 2017
Location: England
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cutler is on a distinguished road
Crocus powder

I am trying to find out the chemical identity of an abrasive that was commonly used in the cutlery industry. It was called "crocus", and its production is described (in an old book) thus;

"Crocus is an oxide of iron, and it is made by calcining copperas (sulphate of iron; the residue is divided into two portions, a bright red powder known as rouge, and a bluish-red powder known as crocus."

I understand that copperas is Ferric (II) Sulphate ( though I am happy to be wrong about that).

Can someone explain to me the calcining process (temperature, levels of atmospheric oxidation, or more simply, can I do this in my workshop using my propane furnace?)?
Even better, presuming that the first product, named in the above quote as "rouge", is a form of iron oxide, what might the chemical name for the second powder be?

For those helpful sould who might resort to google, "crocus" as it is sold now is either rouge, or fine grit aluminium oxide, or the unrefined emery stone powder known as "emery flour", being a natural mix of both aluminium oxide and iron oxides, inter alia.

Many thanks in advance for your help.

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