[Histonet] Ferric ammonium sulfate

[Goetz, Freya E.]

Good morning everyone!
I was wondering if anyone has an opinion on where to buy ferric ammonium sulfate. I want to use it as a mordant for Heidenhain's hematoxylin and I want to buy the solid chemical. I looked for the options on Sigma and the price varies tenfold between options. Most of them are 99% pure so I am wondering what I should be looking for in a mordant quality chemical and what companies are the best for histological reagents.

Thank you for your time!

Freya

Museum Technician
Department of Invertebrate Zoology
Smithsonian National Museum of Natural History
Washington, DC