A while ago I promised to post the recipes for various heat treat salts, but ran into some health problems and forgot all about it! Here's a link to the PDF document. I can't remember who posted the original link to the info or where to find it or else I'd give him credit.
If you mix any of the salts up, be sure to follow all safefty precautions and don't blow yourself up.
www.moonlitforge.com/htsalts.pdf
A cheap source for the Kno3 is fertilizer (potassium nitrate, you can look up the number designation easily). If you want to buy it online, try clayartcenter.net The pyrotechnic or scientific supply houses charge for finely ground grades that arent' necessary.
For high-temp salt, the 50/50 calcium chloride and rock salt works very well, just bake the mix in the oven to drive off moisture before you try and add extra to the molten pool or else you'll get a hell of a steam explosion.