U of S | Mailing List Archive | alt-photo-process-l | Re: potassium and sodium thiocyanate

Re: potassium and sodium thiocyanate

Hi Harlan!
Long time no see (the same Harlan at Photo Form, correct??)!
This is really useful, this water solubility, though in what I will be working on which is a 5% solution I probably won't come up against it.  But now I understand one usefulness of different forms of the thio. The water solubility, for instance, would be understandable when making bleach solutions, or sabattier developer, which both use potassium bromide.
Thio is a fogger, so that is what I am working on. I have both sodium and potassium thio, sodium and potassium hydroxide, and sodium and potassium bromide in my cabinet.  I use the sodium hydroxide in thiourea toning, and was basically wondering if I could use up both forms in the thiourea toning (and both forms of the thiocy in fogging) with the same results.  So I will proceed as if they are interchangeable except doing the weight calculations as DJ said.
I had originally bought the potassium hydroxide for mixing my own lith developer but no longer do that because I find the Fotospeed Lith developer works great.  Likewise, the others I don't use anymore.
Christina Z. Anderson
----- Original Message -----
Sent: Saturday, September 26, 2009 10:49 PM
Subject: Re: potassium and sodium thiocyanate


Often potassium salts tend to be significantly more water soluble by weight than sodium salts. For example,
87g sodium thiocyanate will dissolve in 100ml water while 217g potassium thiocyanate will dissolve in 100ml water.
On the other hand, sodium and potassium hydroxide have roughly equal solubility in water so it is not a universal property.

The trend of often high potassium salt solubility can be useful sometimes though.