The 0.0875 will be the weight of N NOT the volume of N

georgez,

Thanks, but let me just doublecheck this. The 7% is by mass, not volume, but the dilution (1.25 mL/L) is by volume, not mass. If the DynaGro was plain water, it wouldn't matter (1 mL water having a mass of 1 g and all), but I presume that a concentrated fertilizer solution would be denser than water. Is that right, or is the difference too slight to matter?

Cheers!

The key is your use of the word "virtually" you would then say that the specific gravity of the DynaGro solution is 1 & therefore the 7% would refer to the mass of the N in the solution (7 Gm / 100ml)

Alan, I can't tell if you have been satisfied with the answer you got, but in case you haven't, here is a little more information.

In a solution, percent could mean either mass per unit volume or mass per unit mass (or even volume per unit volume in the case of two liquids). Often, there is no indication as to which one is meant.

If you assume the percentage was calculated on a mass/volume basis, you don't have to worry about the density of the solution. As George said, it should contain 7 g N / 100 mL. So your 1.25 mL will contain 0.0875 g N, which translates to 6.25 mmol of N per liter of final solution.

If the percentage was calculated on a mass/mass basis, you will need to know the density of the solution so you can get the mass of your 1.25 mL - at least to be accurate. You could always measure the Dyna Gro with a hydrometer if you really needed its density.

If it was me, I wouldn't worry about the second possibility, because they probably did use the first method, and you wouldn't be off by a whole lot even if they didn't.

ThinMan