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.

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.

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.

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.

But the disulfide should be less polar? At least a little? Nice work!