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How to calculate chemicals/nutrients?

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Old 03-20-2010, 07:09 AM
bratattack bratattack is offline
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Join Date: Mar 2010
Location: Chandler, Az
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Default How to calculate chemicals/nutrients?

Sorry, I have lots of questions and thanks for anyones help in advance. I purchased an ebook from allhydroponics blogspot and it is helpful although I am having trouble with atoms(did not know hydro was so scientific) but anyway heres an insert:

ollowing this, we must calculate how much much K(+) and how much NO3(-) need to be added in order to achieve the concentrations we desire. Since K(+) contains a single K atom, we need 700 mg/L of K(+) in order to achieve 700 ppm of K, for the nitrate ion (NO3(-)), since it contains more atoms, we need to know how much of the nitrate ion is actually nitrogen. In order to do this we calculate what fraction of nitrogen resides in nitrate by relating their molar mases (you can google nitrate molar mass and nitrogen molar mass to get this values or calculate them using your periodic table) . The calculation would be 14/62 which equals 0.22. This means that 22% of each nitrate ion is nitrogen. If 22% of each nitrate ion is nitrogen then we need 200ppm x(100/22) of nitrate in order to get the concentration of nitrogen we want. The result is that we need 909 mg of nitrate per liter in order to achieve our required concentration of 200 ppm.

The problem Im having is the figuring the atoms. I thought I had it and then I was wrong. If anyone can explain this in real peoples terms PLEASE. I thought that if it was 1 element that meant an atom of 1 well apparently sometimes oxygen has anywhere from 1 to 4 atoms????? heres some I found

. In sodium fluoride, there is one atom of sodium and one atom of fluorine. The molar mass will then be:
(1 atom x 23 grams/mole of sodium) + (1 atom x 19 grams/mole of fluorine) = 42 grams/mole of sodium fluoride

2. In potassium hydroxide, there is one atom of potassium, one atom of hydrogen, and one atom of oxygen. The molar mass will then be (1 x 39 grams) + (1 x 1 gram) + (1 x 16 grams) = 56 grams/mole of potassium hydroxide

3. In copper (I) chloride, there is one atom of copper and one atom of chlorine. The molar mass is then (1 x 63.5 grams) + (1 x 35.5 grams) = 99 grams/mole of copper (I) chloride

4. In manganese (IV) oxide, there is one atom of manganese and two atoms of oxygen. The molar mass is then (1 x 55 grams) + (2 x 16 grams) = 87 grams/mole of manganese (IV) oxide

5. In calcium sulfate, there is one atom of calcium, one atom of sulfur, and four atoms of oxygen. The molar mass is then (1 x 40 grams) + (1 x 32 grams) + (4 x 16 grams) = 136 grams/mole of calcium sulfate

6. In magnesium phosphate, there are three atoms of magnesium, two atoms of phosphorus, and eight atoms of oxygen. (The formula is Mg3(PO4)2). The molar mass is then (3 x 24 grams) + (2 x 31 grams) + (8 x 16 grams) = 262 grams/mole of magnesium phosphate

why does oxygen change??? sorry hope it makes sense o someone

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Old 03-21-2010, 09:22 PM
Luches Luches is offline
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Join Date: Jul 2009
Posts: 177

Hi bratattack,

Don't get played by people who want to show off their chemical knowledge, instead of teaching you how to calculate nutrients.

Do yourself a favor and forget about the quoted text and all your examples you have cited, as quickly as possible.

Here is how it actually works in simple terms:
1. Get or take a list of all needed (and appropriate) chemical components to compose nutrients first. No need to know anything about other components or elements that you will not actually need nor use!

2. Inquire the elemental percentage of NPK, Ca, Mg, S, and any other needed trace elements contained in these components only. Actually they are determined by molecular weight, but you don't need to bother as others have done this previously. Get a list...

And here is how it has to be done mathematically:

Example for the elemental content in ppm of potassium phosphate Mono (ppm per 1 gram dissolved in 1 liter of water):

P=SUM (weight in gram*52,2)*0,4364/Liter of water
K=SUM(weight in gram*34,6)*0,83/Liter of water

If this isn't clear yet, again: you have a chemical component called potassium phosphate Mono (or monopatassium phosphate), which is commonly used to manufacture nutrients, it contains Phosphorus and Potassium, OK?

The actual content, as in in how many gram you need per liter to get X ppm is determined by the above formula.

Put these formulas in your spreadsheet and replace "weight in gram" by a corresponding field and one for Liter (as in A1 or B2, - any field of your choice). Put in 1gr of potassium phosphate Mono for 1 liter and you should get:

Phosphorus content of 1 gram potassium phosphate Mono dissolved in one liter of water - P=228 ppm
Potassium content of 1 gram potassium phosphate Mono dissolved in one liter of water - K=287 ppm

These are the basics, from there you can either take any component and use the adequate formula, or you simply get a spread-sheet based nutrient calculator and just fill in the required water and gram.
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Old 09-20-2010, 06:26 AM
alimanzoor35 alimanzoor35 is offline
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Join Date: Sep 2010
Posts: 1

Its really great and sounds good to me alot.

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