# [Wet Thumb Forum]-How to convert % in solution to ppm



## Stratified (Jul 23, 2003)

How does one convert % of a substance in solution to ppm?

I recently began dosing potassium nitrate in my 55 gal planted tank mainly to raise the nitrate levels. I was already adding weekly doses of Leaf Zone, mainly for the iron. Both of these solutions also have potassium.

While potassium is a necessary macronutrient, I'm not sure how much I'm actually dosing since the Leaf Zone only gives the amount of these nutrients as a percentage of the solution.

The dosing calculator suggests the following target levels:

Potassium: 15-20 ppm
Nitrate: 5-10 ppm

I've begun a daily dosing of potasium nitrate which adds 2 ppm of Nitrate and 1.2 ppm of Potassium.

Instead of a weekly dose of 25 ml of Leaf Zone, I've switched to a daily dose of 5 ml (7 days / wk). Leaf Zone label says it is composed of 3.00% soluable potash (K20) and 0.10% chelated iron (Fe).

How can I convert these percentages into ppm so I can accurately measure how much total potassium (and iron) I'm actually adding? Since I don't have a test kit to measure for potassium or iron, I have to infer deficiencies from the condition of my plants. This makes it more important that I track dosing closely.

Thanks.

--Cal Webster

Here to serve...


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## Stratified (Jul 23, 2003)

How does one convert % of a substance in solution to ppm?

I recently began dosing potassium nitrate in my 55 gal planted tank mainly to raise the nitrate levels. I was already adding weekly doses of Leaf Zone, mainly for the iron. Both of these solutions also have potassium.

While potassium is a necessary macronutrient, I'm not sure how much I'm actually dosing since the Leaf Zone only gives the amount of these nutrients as a percentage of the solution.

The dosing calculator suggests the following target levels:

Potassium: 15-20 ppm
Nitrate: 5-10 ppm

I've begun a daily dosing of potasium nitrate which adds 2 ppm of Nitrate and 1.2 ppm of Potassium.

Instead of a weekly dose of 25 ml of Leaf Zone, I've switched to a daily dose of 5 ml (7 days / wk). Leaf Zone label says it is composed of 3.00% soluable potash (K20) and 0.10% chelated iron (Fe).

How can I convert these percentages into ppm so I can accurately measure how much total potassium (and iron) I'm actually adding? Since I don't have a test kit to measure for potassium or iron, I have to infer deficiencies from the condition of my plants. This makes it more important that I track dosing closely.

Thanks.

--Cal Webster

Here to serve...


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## perrush (Feb 24, 2003)

3% K 
= 30 gr K on 1 kg
= 30.000 mg / 1 kg
= 30.000 mg / 1 L (if density =1) (thus a 30.000 ppm solution)
= 30 mg/ml

each ml contains 30 mg K
25 ml contain 30*25 = 750 mg K
if you add that to 55 g (153 L) you've raised the K level of the entire tank by 750/153= 4.9 mg/L = 4.9 ppm

if the 3% means K2O instead of K only. you have to multiply the numbers for K by 0.85 because K2O contains 83% K+
Thus the 4.9 ppm becomes 4.9*0.83 = 4 ppm

similar for Fe, the 25 ml will raise the Fe level by 0.16 ppm

mind that I always say RAISE. So if your tank as already K or Fe levels, the actual conc. in your will be higher.

--
English isn't my native language, but I guess you already noticed that ))
--

Perrush


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## Stratified (Jul 23, 2003)

So,

Convert the % to grams per kilogram or mg/g:
(Assuming density of 1 Kg/l or 1 g/ml ?)

0.03 * 1000 = 30 grams/Kg = 30 mg/g = 30 mg/ml = 30 ppm KO2
0.012 * 1000 = 12 g/Kg = 12 mg/g = 12 mg/ml = 12 ppm Fe

I appreciate you walking me through the calculation. Can't we just multiply percent as a fraction times 1000 to get ppm?

Now adjust for K in KO2:

0.83 * 30 = 24.9 ppm K
0.17 * 30 = 5.1 ppm O2

What happens to the oxygen in the K02?
Since it's not pure K, does all of it disolve and is it available to the plants?

So, my daily 5 ml dose of Leaf Zone adds:

K: 24.9 mg * 5 * 7 = 871.5 / 208L = 4.19 ppm /wk
Fe: 12 mg * 5 * 7 = 420 / 208L = 2.02 ppm /wk

(I think 55 gal = 208L)

Add in K from my KNO3 dose:

4.19 + 8.4 = 12.59 ppm /wk

Does this sound right?

Thanks! Now I know my total weekly dosing:

Total weekly Ferts:

NO3: 14.00 ppm
K: 12.59 ppm
Fe: 2.02 ppm

--Cal Webster

Here to serve...


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## perrush (Feb 24, 2003)

ppm = mg/L , not mg/ml

so 30 mg/ml is not 30 ppm but 30 000 ppm

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there is actual no K2O (and not KO2) is the bottle, it's just an international way to expres K concentration.

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the Fe would be 0.0012 instead of 0.012
so your 2.02ppm will be 0.202 ppm/wk

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I hope it is 0.1% Fe and not 0.1% chelated Iron because chelated iron contains only 6 to 13% Fe (depending on the sort of chelate). If so, that would drag the Fe content down from 0.1% to 0.006% or 0.013%

------

55 gal = 208 L ?? ofcours, my fault

-----

for the rest looks it ok

--
English isn't my native language, but I guess you already noticed that ))
--

Perrush


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## PlantumOfTheOpera (Mar 13, 2003)

Perrush,

I have been trying to follow your posts re converting % to ppm.

Cal mentions Fe as .10%
but the calculations look like .12%???

I'm lost! I have a fert that I want to do the same calculations with, but cannot follow what happened here. My fert says it has .6% FeEDTA

How would I get the ppm?

By the way, I see you're from Belgium; Heffe is great beer!

POO


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## Stratified (Jul 23, 2003)

Sorry, I should have followed up with a corrected Fe calculation. I can't remember now why I used .12% vice .10%.

Convert % to ppm:
0.0010 * 1000 = 1.0 g/Kg = 1.0 mg/L = 1.0 ppm Fe

Calculate weekly dose:
Fe: 1.0 * 5 * 7 = 35 / 208L = 0.168 ppm / wk

The conversion from % to ppm is still a little fuzzy to me too.

--Cal Webster

Here to serve...


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## perrush (Feb 24, 2003)

1% = 10 gr/L = 10 000 mg/L = 10 000 ppm
(only if the density of the solution is 1, which is in most cases)
easy enough ? 

an 6% Fe-EDTA is 60 000 ppm Fe.
make a 10% solution of it (100 gram in 1L) and it has 6 000 ppm Fe ...
6 000 ppm means 6 000 mg/L or 6 mg/ml.
so 1 ml of a 10% solution contains 6 mg Fe.
or 10 ml of that somution would raise a 100 L tank by 0.6 ppm because it brings 60 mg in 100 L

ect ...

--
English isn't my native language, but I guess you already noticed that ))
--

Perrush


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## Stratified (Jul 23, 2003)

Okay, I get it now. Thank you! That's crystal clear. That's what I was looking for in terms of a description.

--Cal Webster

Here to serve...


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## PlantumOfTheOpera (Mar 13, 2003)

Thanks for the reply guys, ... But I'm still confused:









{.01) = 1% solution = 10 ppm per Cal
{.01} = 1% solution = 1000 ppm per Perrush

Which one is it?

One more time for the mathematically impaired please!

POO


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## Stratified (Jul 23, 2003)

Perrush's last message was giving a general descripiton of how to convert % of solution to ppm. Then he offered examples using round numbers to simplify it.

My corrected calculation related directly to the level of iron in the Leaf Zone (0.10%) and my daily dosing of it in my 55 Gal aquarium.

To substitute my specific Leaf Zone % iron in his example, using his 100L tank:

1% Fe-EDTA is 10 000 ppm Fe.

make a 10% solution of it (10 gram in 1L) and it has 1 000 ppm Fe ...

1 000 ppm means 1 000 mg/L or 1 mg/ml.

so 1 ml of a 10% solution contains 1 mg Fe.

or 10 ml of that somution would raise a 100 L tank by 0.1 ppm because it brings 10 mg in 100 L

---Now, adjust for my 208L (use 200L for round number) tank:

or 10 ml of that solution would raise a 200 L tank by only 0.05 ppm because it brings 10 mg in 200 L (diluted by half).

So, for weekly dosing calculations, adding 5 ml of a 0.10% solution of iron to a 208L tank daily:

1 mg * 5 ml * 7 days = 35 / 208L tank = 0.168 ppm per week

Does this sound right?

If not, hopefully Perrush will correct me.

================================

Not to confuse things, but Perrush made mention of the reduced effectiveness of chellated iron. The calculations I made were based on the assumption that the full 0.10% of Fe was available. If not, I'd have to recalculate to get the correct dosage in ppm.

From the Leaf Zone label:

Guaranteed Analysis: 0-0-3
Soluble Potash (K20).....3.00%
Iron (Fe)................0.10%
0.10% Chelated Iron (Fe)
Derived from: Potassium Sulfate and Iron EDTA

--Cal Webster

Here to serve...


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## perrush (Feb 24, 2003)

> quote:
> 
> make a 10% solution of it (10 gram in 1L) and it has 1 000 ppm Fe ...


make a 10% solution of it (10*0* gram in 1L) and it has 1 000 ppm Fe ...

--
English isn't my native language, but I guess you already noticed that ))
--

Perrush


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