N from Nitrate 15.5%
Nitrogen is 23% of NO3
0.155/0.23 = 0.67 = 67% by weight of NO3
N from Ammonia is 1%
Nitrogen is 82% of NH3
0.01/0.82 = 0.0122 = 1.2% by weight of NH3
1 gram of powder therefore will consist of 0.67 grams of NO3 and 0.012 grams of Ammonia.
ppm (parts per million) is defined milligrams of solute (powder) / kilogram of solvent (water).
So putting 1g (1000mg) of powder (which has 670mg NO3) in 0.5Kg of water nets you 670mg/0.5Kg = 1340ppm NO3 in your solution. That's the strength of your solution. It will also have 12mg/0.5Kg = 24ppm of Ammonia in the bottle.
Now, lets just look at how much NO3 and NH3 will be dosed with each mililiter. 670mg NO3 is divided evenly into 500ml of water, so each ml of solution delivers 670mg/500ml = 1.34mg NO3 per ml of solution. It also delivers 12mg/500ml = 0.024mg NH3 per ml.
If this is a CO2 injected tank, and if we intend to follow Barr's reference values of 20ppm per week in 3 even doses, then each dose should deliver roughly 7ppm per dose.
A 2gal (8L) tank doesn't really have 2gal of water in it but I'll use that number for the calculations and adjust it later because we want to look at the implications of adding NH3. If we were not using a mix with NH3 I would never consider this factor.
Again, the ppm calculation is: Solute-mg/Solvent-Kg and we want the value to equal 7ppm. So:
Solute-mg/8kg = 7ppm ==> Solute-mg = (7ppm)*(8Kg) = 56mg
Since each ml of solution delivers 1.34mg of NO3 we need 56mg/1.34mg = 42ml per dose.
Now let's check how much ammonia we are adding with this dose:
42ml @ 0.024mg NH3 per ml = 1.01mg NH3 per dose.
1.01mgNH3/8Kg = 0.126ppm NH3 per dose. This is a LOT, as Ian pointed out. It's about 4 times higher than the EPA recommended amount. But there are so many factors. There is a reaction that occurs where NH3 ionizes and become NH4, which is about 50 times less toxic than NH3. How much of the NH3 that ionizes into NH4 depends on pH of the tank. At low pH there is a high ionization rate but at high pH the ionization rate is lower. The toxic effects are more severe at higher temperatures. The microbes in the tank, as well as the plants convert or consume NH3/NH4 rapidly, so that if the tank is mature, the exposure to toxicity is less than if the tank is immature. If the tank is CO2 injected then the pH will fall, reducing the toxicity, but by how much is dependent on injection rate as well as the buffering of the water, so water with high alkalinity (KH) will have less pH drop and soft water will have a deeper drop in pH and lower toxicity.
If this is a non- injected low tech tank then you may be playing with fire as the pH tends to be higher, generally speaking.
I think to be on the safe side, to start with, if this were your only option for a CO2 injected tank, I would add not more than 1/5th gram of powder to the 500ml of water. You may want to make a further reduction to adjust for the fact that you do not really have 8L of water, typically there is only 80% of the rated tank size due to gravel, rocks, plants and fish. So you could reduce the powder amount by another 20% or use 20% more water in the solution.
Remember that EI dosing schemes are all about CO2 injected tanks. If this is a low tech tank then you should reduce these values by another 5-10 times.
Cheers,