I have to bottles of Lamy blue-black fountain pen ink. It turns out that some months ago the composition of the ink was changed by the manufacturer and there is no difference in the package. Before, this ink used to contain Iron-Gall. Which makes the ink more permanent (old inks contained most of the times Iron-Gall). As Iron-Gall is an oxidizer, it has been removed from the ink because it can damage the pens if not cleaned regularly.
I don't know much about chemistry and I wonder if any of you could tell me a way to know if my ink has Iron-Gall and therefore is safe for long lifespan documents. I was wondering if litmus paper would do the trick comparing this ink with normal black ink (which does not have Iron-Gall).