[barrel browner]

Hi All, Ferric Chloride these days is made with Mill Scale and Ferrous Sulphate, can someone explain to me how to make a 50% strength Ferric chloride solution using the old process.

[Borek]

Is this question in any way different from the one you asked here:

https://www.chemicalforums.com/index.php?topic=113091.0

In general, if it is the concentration that is a problem (you never confirmed) you can always try to evaporate some of the water (just heat the solution up and wait).

Also: I have no idea what the "old process" is.

[barrel browner]

I use it for a metal finish which is a rusting process so the ferric is mixed with acid, alcohol and copper sulphate, we have had issues with coppery patches on our finish spoiling the black colour.  We have a small amount of old stock Ferric Chloride that works fine,  around 8 years ago they switched to making it by mixing mill scale with ferrous sulphate, I believe the old process was iron and Hydrochloric acid, so I am looking for someone who can advise me on where to get it or how to make it myself, we always used to buy it in 50% strength.

[Borek]

You can always try to buy solid FeCl₃ from chemical suppliers, like Sigma-Aldrich, and make the 50% solution by yourself.

Trick is, devil may be in the purity - reagent grade ferric chloride is about 98% pure, and the other 2% are not well defined, yet they can be crucial for your application. The only sure way of checking it by trial and error.

[barrel browner]

Thank you would this have still been made using the mill scale process?

[Borek]

No idea.

Note: in most cases when it comes to reagents it doesn't matter how they were produced - a compound is a compound, no matter where it does come from. Things like concentration, pH, presence of other reagents recipe calls for are much more important. In practice sometimes (rarely, but often enough it is always a thing to remember) minute amounts of byproducts (which do depend on the production method) can influence the output of a process. The purer the reagent, the lower chances of the problem - but purity typically comes at a hefty price.

As I wrote earlier - the only to make sure it works is to try.