What can I do with Potassium ferricyanide?

I just bought a darkroom or 3 wirth of stuff and in it I found a nice jar of Kodak Potassium ferricyanide.

How would I use this in developing b&w film. Particularly, very expired tri-x. Aa in 60 years old.

Any other fun stuff I can do with it?
Thanks

It is useful for bleaching. Typically for bleaching highlights to gain the white of the base.

See for Farmer reducer.

It is also used in the making of cyanotypes. A method of making prints that does not use silver.

very diluted bleach with it can be used for selective latent image bleach.

Can also be used for rehalogenation bleaching, and bleaching of colour materials.

It is a part of the iron blue toner too.
http://unblinkingeye.com/Articles/Blue/blue.html

Hello,
together with sodiumthiosulfate it is the Farmer reducer. Together with potassiumbromide it is the bleach for sulfur toning with sodiumsulfide- or thiocarbamide-toner. It cannot be used in any developer as it is an oxidating agent, all developers are reducing agents.

Gerald C Koch said:

It is also used in the making of cyanotypes. A method of making prints that does not use silver.

Click to expand...

and are a huge amount of fun to make !

I used to use this quite often in the darkroom for localized hilight boosting. You can also use it as a bath to affect all hilights. For local work, you need to be slow with it and build the effect. I would typically apply a little bit of solution to the desired area, wait a few seconds and then apply fixer with a sponge to arrest the bleaching. The effect can go too far really fast, if you see the look you want as your applying it, it's going to continue on too far and you'll have to start over with a new print (ugh).

Safety discussion here: (there was a url link here which no longer exists)

HTH,
CB

Bleaching the highlights to give the print more pop.