First of all, VERY IMPORTANT!!! : TOO MUCH copper will KILL your plants. no Joke. So please, please, please, if you use this recipe you must have a VERY accurate scale. something like a jewelers scale that measures grams to at least one decimal place.
This recipe is for
1 gallon of homemade RootZone DM
first of all, when buying copper sulfate, there a couple different formulations for that particular chemical. so, what I have done is this: The following link is for 500 grams of copper sulfate pentahydrate
CHEM CU SULFATE PENTA ACS 500G - Laboratory Chemicals - Laboratory Supplies - 8EJ50 : Grainger Industrial Supply
The molecular weight of copper sulfate pentahydrate is 249.68
The molecular weight of copper is 63.546
divide 63.546 by 249.68 and you will find that copper sulfate pentahydrate is 25.6% copper. If you use another form of copper sulfate, make sure that you know the molecular weight of the compound which you can find using a periodic table. the reason I say this is that there is also Copper(II) sulfate (cupric sulfate) which has a higher percentage of copper because it is not hydrated.
Anyway, for
1 gallon, you will need exactly
15.14 grams of copper sulfate pentahydrate which is 1.024 grams of elemental copper per liter of water and thus 3.88 grams of elemental copper per gallon
1.024 grams elemental copper per 1000 ml RO water equals .1% soluble copper.
The amount of potassium nitrate in that stuff is negligible. I don't even know why it is in there. They use roughly 13 grams of potassium nitrate per gallon which does not contribute to the potassium or nitrogen content of your nutrient solution much at all.
So, just throw in 13-14 grams per gallon of potassium nitrate (saltpeter) and you will have roughly .06% nitrogen and .15% potassium
you can get potassium nitrate just about anywhere. you can get it on ebay for about $5 a pound all day long and most of the stuff listed on ebay is refined and high quality....much more pure than what is needed for this recipe.
anyway, to re-cap this recipe for
1 gallon of homemade rootzone DM:
use
15.14 grams of copper sulfate pentahydrate
13 grams of potassium nitrate
and
1 gallon (3785) ml pure RO water
There you have it. 1 gallon of RootZone DM for pennies!