# calculating percentage to ppm



## kenneth_kpe (Oct 1, 2005)

I have a bottle of chelated iron at 5% concentration... I had a bookmarked site before that contains all the formulas to convert these things... I could not find it anymore so can anybody give me some help with the formulas ?

Lets say if i add 1 ml of the 5% concentration formula, how many ppm of Fe am i adding to a 35gal tank ?


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## hoppycalif (Apr 7, 2005)

One ml of a water solution is about one gram of mass. So, your one ml of iron solution is one gram of solution, which is 5% Fe. That means one ml is .05 grams of Fe, which is 50 mg. 50 mg divided by 35 gallons, which is 35 times 3.785 liters. So, you have 50 divided by (35 times 3.785) = .377 mg per liter of iron.


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## kenneth_kpe (Oct 1, 2005)

oh man. head ache.. 

so an ml would add roughly .377 ppm of Fe into a 35 gal tank.. so i should dillute this..

i should mix roughly 3 ml of the chelated iron mix with 100 ml of distilled water so I can get roughly .1 ppm for every 4.5 ml i dose.. correct ? 

I based my numbers on the fertilator using the 10% DPTA iron


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## kenneth_kpe (Oct 1, 2005)

any help ? i hope my calculations are correct hehehehe


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## JonnyThe (Apr 27, 2007)

I think it should be 5.888 ml added to enough water to bring total volume to 100 ml. That's for a 4.5 ml dose.

I used the typical chemistry equations instead of the fertilator to get the above answer. I'm writing a program to do these sorts of dilution calculations.


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## kenneth_kpe (Oct 1, 2005)

hi johnny do you know a site where I can find these basic chemistry equations presented for a non-chemistry oriented person ?


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## JonnyThe (Apr 27, 2007)

kenneth_kpe said:


> hi johnny do you know a site where I can find these basic chemistry equations presented for a non-chemistry oriented person ?


No I don't sorry. Other members may be able to help with that. I can try to explain one way of working it out though. Hopefully there's no mistakes 

For a lot of dilution calculations, the important formula to remember is:

m = cV

where
m is the mass, in milligrams
c is the concentration, in mg/L, or ppm
V is the volume, in Litres

You can rearrange this formula to also obtain c or V from the other two values:

c = m / V, and
V = m / c

Now, you want 0.1ppm iron in 35 gallons. Remember that ppm and mg/L mean the same thing.

So let's work out the mass of iron required for a single dose:

c = 0.1ppm = 0.1mg/L
V = 35 gal = 132.475 L

plugging these values into the above formula gives:

m = cV
= 0.1 mg/L * 132.475 L
= 13.2475 mg

This is the mass of iron required in a single dose to obtain 0.1ppm in your 35 gal tank.

But you need to know the volume of your iron mix which contains 13.2475 mg of iron:

Your stock solution has a concentration of 5%. As Hoppy said, this means that 100 ml of it will contain 5 grams of iron. So 1 Litre would contain 50 grams, or 50,000 mg. This gives a concentration of 50,000 mg/L. We're just getting the correct units for the formula here; that is: mg and litres.

Rearrange the formula to find the volume:

V = m / c
= 13.2475 mg / 50,000 mg/L
= 0.00026495 L
= 0.26495 ml

Ok, so this means 0.26495 ml of the chelated iron mix would need to be added to your 35gal tank to get 0.1ppm of iron.

But you want to be able to add 4.5 ml so it's easier to measure, and you want a dosing solution with a total volume of 100 ml.

So that means your dosing solution will have:
100 / 4.5 = 22.222 doses.

But a single dose is 0.26495 ml. So multiplying 0.26495 by the number of doses will give you the total volume of your iron mix needed to make up the 100ml dosing solution:

V = 0.26495 ml * 22.222
= 5.888 ml

So, to make your solution, add the 5.888 ml of iron mix, and add enough distilled water to give a total volume of 100ml.

Obviously measuring 5.888 ml would be a bit difficult even with a chem lab. But if you rounded it to 6 ml, it would only give about 1.9% error in your final solution.

I probably have just confused you. But I like doing it this way since once you know what the volume of a single dose is, any required dilution may be calculated easily: just multiply the single dose (eg 0.26495 ml) by the volume of the solution you're making (eg 100ml), then divide by how much of it you want to dose (eg 4.5 ml).

So if you wanted to make up 250 ml of dosing solution, and you wanted to be adding 5 ml of it each time, you would need:

0.26495 * 250 / 5 = 13.2 ml of the iron mix, made up to 250ml total volume.


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## kenneth_kpe (Oct 1, 2005)

i will absorb this when i get home ! haha wish me luck...

(im in the office, people might start noticing that im not working haha)


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## kenneth_kpe (Oct 1, 2005)

hey I just read it right now, understood it perfectly ! thanks super ! hehe time to dose !


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