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Re: potassium and sodium thiocyanate

  • To: alt-photo-process-l@usask.ca
  • Subject: Re: potassium and sodium thiocyanate
  • From: Dirk-Jan Treffers <dirkjan.treffers@gmail.com>
  • Date: Sat, 26 Sep 2009 18:41:23 +0200
  • Comments: alt-photo-process mailing list
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Hi Chis,

Sodium and Potassium salts are in essential interchangeable, a bit depending on what your intended use is. It's the same as with Potassium and sodium hydroxide: It's the anion that's what you're using the stuff for (i.e. hydroxide, or thiocyanate, the kation is pot or sod).
Chemically, it's KSCN or NaSCN

However, do keep in mind you need different weigths of the same chemical.
You will need the same number of molecules for you reaction, but since potassium has a higher atomic weight than sodium, there's a difference in moleculair weigth between PSCN and NaSCN:
PSCN: 97.181 gr/mol (potassium thiocyanate)
NaSC: 81.072 gr/mol (sodium thiocyanate)
(mol doesn't stand for molecule, but for a unit, it's defined as the numer of molecules that are present in 12 grams of carbon, but just forget about that ;-)  )

basically: if you need 1 gram of PSCN, you will need 0.834 grams of NaSCN to have the same strength. (since P is 'heavier' than Na, you need less of it, to have the same amount of thiocyanate ions)
The other way around: for 1 gram of NaSCN, you will need 1.1987 grams of PSCN (again, because, Na is 'less heavy' than P, you need more NaSCN in order to have the same amount of thiocyanate ions)

(the reason i wirte 'heavier' in quotes, is that, chemically speaking, this is the wrong way of stating things. The wright way would be: has a higher density..)

Okay. I'm drifting away towards my old profession (teaching at the chemical faculty of Utrecht University), here's the short answer:

Yes, they are interchangeable.
Use the follow correction to change between them:
1 gram pot-thiocyanate equals 0.834 gram sod-thiocyanate
1 gram sod-thiocyanate equals 1.1987 gram pot-thiocyanate....

(sorry for you 'weird' americans with your non-metric system, but the same correction factors apply to ounces, pounds and stuf as well :-)  )

hope this is enough (or maybe too much) information for you!

kind regards,


(dirk-jan, but that's mostly unpronounceble by non-dutch speakers.. Spanish folks call me Juan, Italians refer to me as Julio...Again, probably too much information ;-)  )

2009/9/26 Christina Z. Anderson <zphoto@montana.net>
Dear All,
Away from the list for a month or so just to wrap my head around the new semester, a new Director of the school, a new faculty hire (all GREAT things), and writing writing writing...I just don't know how some of you keep up on UTube, web surfing, twitter, Facebook, MySpace, lists, forums, etc. etc.

Anyway, I actually have had time to clean out my chemistry stockpile and was wondering if chemists on this list could tell me if sodium and potassium thiocyanate are essentially interchangeable?

Potassium and sodium hydroxide?

Christina Z. Anderson