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What do we know about Iron Chromate?

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I've got some Iron Chromate, and never knew what to do with it. 

Just saw in this thread on making grey glazes that it's 'fairly toxic' - anyone have more info on that 'fairly? 

  • Is it problematic as dust, so during the measuring/mixing?
  • During actual glazing, through skin exposure to wet glaze? 
  • As fumes during firing - inhalation?
  • Or will it leach post firing, even when it's encased in a stable glaze?

Any info/sources much appreciated!

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Iron chromite is a synonym for iron chromate. If you have to have a similar colour response it's far safer to use iron oxide + chrome oxide. Iron chromate is highly toxic through absorption, inhalation and ingesting. I agree with Mark, take it to the toxic waste drop off.

@kristinanoel, some reading on chrome and it's various forms below. 



edit: my comment about iron chromite being a synonym for iron chromate is referring to the reference I linked here from the National Center for Biotechnology.

Edited by Min
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Iron Chromite and Iron Chromate are similar in the sense that they are both a combination of Iron and Chromium. However they are two very different compounds. And in Chemistry, those differences matter a great deal.

Iron Chromite: FeCr2O4.

Iron Chromate: Fe2(CrO4)3

I'm by no means an expert in chemistry, but I'm going to say I'd agree with liambesaw that Chromite is safer then Chromate. However, I personally would use neither. Since they both contain Chrome. And Chrome isn't great health-wise. 


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6 hours ago, liambesaw said:

Chromate is hexavalent chromium,  iron chromite is not.  They are not synonymous, that's the confusion I am referring to above. 

Iron chromate, highly toxic, water soluble, carcinogen.  

Iron chromite, slightly toxic, insoluble, not carcinogen.

From wiki the issue seems to be not the in the ground form of chromite but what happens to it during the mining process. Perhaps I'm reading this wrong but from what I'm taking from it is the chromite during the processing of it under normal processing conditions and not a wet and non-oxygenated atmosphere converts to the hexavalent state. From the Health Effects section of this link:

"Chromite ore is found in underground conditions. Therefore, when exposed to aboveground conditions, various effects will occur. Some of these effects include weathering and oxidation. The element chromium is most abundant in chromite in the form of trivalent (Cr-III). When chromite ore is exposed to aboveground conditions, Cr-III can be converted to Cr-VI, which is the hexavalent state of chromium. Cr-VI is produced from Cr-III by means of dry milling or grinding of the ore. This mostly has to do with the moistness of the milling process as well as the atmosphere in which the milling is taking place. A wet environment and a non-oxygenated atmosphere are ideal conditions to produce less Cr-VI, while the opposite is known to create more Cr-VI.[19]"


Edited by Min
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Sure, it can be converted, this is how iron chromate is made.  It is not the same compound though.  It would take quite a long time, or heat, or both to convert chromite to iron chromate. 

The very simple way they can be separated though is that iron chromite can be rinsed, since it is not soluble, and the chromate would be rinsed away leaving chromite.  It's not a huge part of industry however since chromite is mined to make stainless steel, and they don't care what form it is in.

It would be the same as saying red iron oxide and black iron oxide are the same thing.  Because if you oxidize black iron oxide(magnetite) in air, it turns to red iron oxide (hematite). 

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