i just use the store bought stuff which is %3
then dilute that to about 1/20 or 1/10
just a few drops in a glass of water helps.
Some say there are other chems used in it as buffers, but i have used it %50 out of the bottle on seedlings with no ill effects
(as a test)
and have used it on a drowned papaya plant (root-rot) straight from the bottle.
it helps root rot a bit, but only for a short time. if you are able to dry out the roots after, its a good idea.
if not, you just prolong the inevitable.
i doubt it does much to help germinate, though, there could be some very slight breakdown of the seed-coat.
i just use it to keep the fungi/mold away with seeds and seedlings
in a very dilute solution.