A Modern Method for Manufacturing Ferric Oxalate

[Ian Leake]

This post is for people interested in making their own ferric oxalate for platinum/palladium printing.

Most people buy their ferric oxalate from one of the specialist photographic retailers. However, I find that the best ferric oxalate is the one I make myself.

I have been working on a better way to make my ferric oxalate. It's much easier and less messy than the traditional process used by Pizzighelli and others. So far I've had very good results, with some of the best blacks I've ever made.

This process is not new to science, but doesn't seem to have made its way into the photographic community. It is based upon US Patent 1899674: “Process for the production of ferric oxalate” filed by Leo Curtin in 1933 and now expired. A more complicated version of the process was published by Dick Stevens in Making Kallitypes (1993). Stevens' process produces sulphuric acid as a by-product, so really is not suitable for small scale production.

In summary, you add oxalic acid then hydrogen peroxide to iron(ii) oxalate in water. It's easy, clean, and makes high quality ferric oxalate.

Full instructions are here on my website: https://www.ianleake.com/pages/a-modern-method-for-manufacturing-ferric-oxalate

 

[simongg]

I found another table online that corresponds to the specific gravity and content of iron oxalate. It's different from yours. Which one is correct? thank you.

 

[simongg]

I found another table online that corresponds to the specific gravity and content of iron oxalate. It's different from yours. Which one is correct? thank you.

A short treatise on Iron Salts – AlternativePhotography.com

www.alternativephotography.com

 

[Ian Leake]

I found another table online that corresponds to the specific gravity and content of iron oxalate. It's different from yours. Which one is correct? thank you.

A short treatise on Iron Salts – AlternativePhotography.com

www.alternativephotography.com

They're both correct, but measure different things. If you base your %wbv calculation on the commercially available dry powder, then you aim for about a 27% solution. If you base it on the actual iron(iii) oxalate content then you aim for about a 20% solution. The bottom line is to aim for a specific gravity of about 1.18 and then be consistent.

 

[simongg]

它们都是正确的，但测量的是不同的物质。如果你根据市售干粉计算%wbv，那么目标溶液浓度应为27%左右。如果你根据实际的草酸铁(iii)含量计算，那么目标溶液浓度应为20%左右。最终目标是比重约为1.18，并保持一致。

Thanks