Potassium - Sodium thiocyanate interchangable?

[cinejerk]

Is it ok to interchange sodium and potasium thiocyanate for bw reversal processing.
If so how much more or less should be used if sodium thiocyanate is used?
thanks

 

[Photo Engineer]

Used in the developer, and if you correct the amount used for the molecular weights of Na or K, yes they can be interchanged.

They cannot be interchanged in fixers. Potassium compounds should never be used in fixers.

PE

 

[cinejerk]

ok thanks. Yes it was for use in the first developer.

 

[Lowell Huff]

Thiocyanate is a silver solvent. When used in the first developer, it removes information from the toe of the curve. Another way to describe this effect is that it increases contrast by removing shades of grey. This chemical is important in processing Microfilm where the desired result is black and white (high contrast). If you leave it out, you can process for continuous tone, even with reversal processing.