[Samuel Johnson]

Hi all, I have used for many years sulphate of iron as part of a process for a metal finish, it worked perfectly for years but now does not, we are sure the problem is with the sulphate of iron, has the way this is made changed in any way in the last few years? does anyone know of somewhere I can get help with this? thanks in advance.

[Arkcon]

The chemical iron sulphate hasn't changed its formula recently.  And by recently, I pretty much mean "since the universe formed."  However, its possible the batch you have is contaminated or has some other problem, such as poor dissolving characteristics or something like that.  You can tray to have it characterized, and compared with a good batch, or just ask the vendor to replace this batch.  You can try to determine the fitness of purpose for any batch you get yourself -- get a clean flat piece of metal, and go through the process.  You can do this for a good batch, or  a marginal batch, and then eventually detect a bad batch before you even start.