calcium test kits

[happychem]

Forget the mole thing, I think that there's some problem with comparing umol/mol to mg/L, I can't figure it out right now (as much as it pains me to admit it ) but there's definitely something wrong with the conversion between them.

Anyway...

From what I work out, the code you've posted actually sais that 1g of KNO3 added directly to a 100L tank will increase NO3 by 6.13ppm. To calculate how much 1mL of solution would add one would need to know how many mL of water was used to prepare this solution. So if, for example, 1g of KNO3 was added to 100mL of water, then 1mL of this solution would increase the NO3 of a 100L tank by 0.0613ppm.

I'm with ya

In a general case:
PPM = desired increase in ppm (mg/L)
PCT = Percent weight of compound of interest expressed as a decimal
TankSize in L
Then the amount that needs to be added, in grams to increase the concentration by a desired mg/L:

Mass to add (g)=[TankSize(L)/PCT]*PPM(mg/L)/1000(mg/g)

This is what I meant about your original equation, the 1000 is a conversion factor between mg and g so that the mass of X to add is in grams, not milligrams. Did I make a mistake? I'll admit to being pretty tired.

 

[reiverix]

ok I'm confusing myself now

What the formula does it this. If you add one gram KNO3 to 1ml water, it will raise a 100 liter tank by 6.13ppm nitrate. So that's the second formula I posted based on Chucks. For example

TankSize = 100
GramsToAdd = 1
PCT = 61.32;
GramsOfChem = GramsToAdd * ( PCT / 100 )
GramsOfChem = 0.6132
PPMInLiter = 0.6132 * 1000
PPMInLiter = 613.2
EachMlAdded = PPMInLiter / TankSize
EachMlAdded = 6.132


And now for the first formula I posted to calculate grams from current and target PPM. Based on the above figures.

CurrentPPM = 0
TargetPPM = 6.132
TankSize = 100
PCT = 61.32
GramsToAdd = (TankSize / PCT) * (TargetPPM - CurrentPPM) / 10
GramsToAdd = (100 / 61.32) * (6.132 - 0) / 10
GramsToAdd = 1.631 * 6.132 / 10
GramsToAdd = 1


Voila, but a second opinion would be appreciated

 

[happychem]

ROFL!!! When I figured it out, I fell over laughing.

The first one works because you're adding your 1g to 1mL, then adding 1mL to the tank. In other words, you're adding the 1g directly to the tank. Dig?

The second was the part that had me frustrated, pulling out my hair, because I was getting the exact same numbers using my equation but I couldn't figure out why yours looked wrong, then I figured it out.

Your equation is right, but it sneaks a unit through that I didn't catch.

Normally I do things piece by piece to keep track of each unit, this means looking at percentages as a decimal, not a percent. The part that kept throwing me for a loop is that the tank volume in the example is 100L and your example shows the 61.32% divided by 100, which is what would normally be done to convert the % to a decimal. But since you're keeping it as a full percentage, then your 1000mg/g (to convert grams added to mg/L) is reduced to 10:

1000mg/L divided by 100% = 10.

:dance :dance

All is right once again

 

[daveedka]

Could someone please explain why I find this very exciting, and John since I never got your calculator to work, does it do table salt ? Just curious.
dave

 

[happychem]

Well, the exact same calculation would work for any salt, be it NaCl, CaCl2, or KNO3, as long as you know the mass percentage of the ion of interest.

As for the excitement, I can't explain it, but I can agree that I felt a huge weight lifted when I figured out why two seemingly different equations were both right and both produced the same answers.

 

[reiverix]

ok then say I wanted to do the following......

We have 323 liters of water. We want to raise KNO3 by 10ppm. I calculate 5.27 grams. Happychem, do you concur?

 

[happychem]

I concur.

 

[reiverix]

Sigh of relief for me then I would have hated giving out the wrong numbers especially for dosing. Is 'concur' a word or did I make that up from somewhere

Normally I do things piece by piece to keep track of each unit, this means looking at percentages as a decimal, not a percent.

Yes, that would be the sensible thing to do.

 

[happychem]

No, it's a word, a good one too.

Both the equations that we're using are exactly the same, the only difference is that I'm dividing my percentage by 100 as a matter of course, you left it in, so the 100 just came out of the unit conversion.