bigbob7777, use Tom Clothier's Germination Database for that information
http://tomclothier.hort.net/page02.html

I soak all my seeds in a potassium nitrate solution for about 15 minutes before I plant them. This also gives me a chance to see which seeds are floaters which I usually discard unless I don't have any extra seeds of that variety.

Interesting. So how does potassium nitrate work compared to water, citric acid or peroxide soaks? Does it work as good or better with hard seed coats?

Where does one get potassium nitrate?

I've seen potassium nitrate mentioned on several websites as a seed soaking alternative but I've not seen any suggestions as when or how to use it instead of water or other soaking methods.

Followup post: I bought a 50 pound bag of potassium nitrate for $26.32 three years ago at Orange County farm supply, so it costs about 53 cents a pound. That 50 pounds would probably make enough solution to soak a million seeds. I put about a quarter teaspoon in a couple of ounces of water.
Potassium nitrate among other things is used for fertilizer and making gun powder. Supposedly it simulates the seed passing through the digestive system of a bird, plus it gives two essential nutrients, particularly nitrogen in the most immediately usable nitrate form.

I typically only soak the seeds which i can tell have thick seed coat, like Morning Glory's and Lupines. I can't recall ever soaking anything else.

Thanks for the info. So it sounds like potassium nitrate is inexpensive and readily available at farm suppliers. That's good to know.

I'm soaking juniper seeds in plain water now and from what I've read they should soak for about 4 or 5 days for the water to soften the very tough seed coat. Maybe a shorter soak in potassium nitrate might help soften the seedcoats and improve germination?