Regarding my previous post I just wanted to say that it is not meant to inflame or to put doubt on Kodak's high quality and Q.C. which is above reproach.

Regarding Natrium vs Potassium PE already said it they are pretty much interchangeable. Agfa and other german manufacturers prefered potassium because they were usually part of a chemical giant (IG Farben and later Bayer Leverkusen) or companies (Perutz, Dr. Schleussner) and potassium was readily available and often a byproduct of other chemical manufacturing processes. The old german name for potassium is potasche or pot ash it's history is rather bloody literally (burned animal bones) just like the old german name Potassium hexacyanoferrate is Blutlaugensalz or Bloodlyesalt (made from mostly oxblood). The old chemical names are often very interesting and tell the history of the product.