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Author Topic: Help Calculate a Dilution of Calcium Chloride  (Read 10871 times)

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LyreTail

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Help Calculate a Dilution of Calcium Chloride
« on: December 01, 2007, 01:47:14 PM »

CaCl2+2H2O

I am having trouble calculating a dilution of Calcium Chloride to attain a certain mg/l inside an aquarium for plant fertilization reasons. The goal is to raise the water to a minimum of 5 mg/l

For example
How many tsp of calcium chloride do you need to dilute into a 1 liter botle of water in order to make a dilution that will increase the Ca in ten gallons of water by 10mg/l if you only add 10 ml of the dilution to the ten gallons of water?

I wish to have the "1 ml = 1 mg/l increase in 10 US gallons of water" formula because this is an easy formula to deal with.

Thanks in advance for any time you can give this problem

Curtis

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Borek

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Re: Help Calculate a Dilution of Calcium Chloride
« Reply #1 on: December 01, 2007, 10:13:49 PM »

I wish to have the "1 ml = 1 mg/l increase in 10 US gallons of water" formula because this is an easy formula to deal with.

Start converting 10 gallons to L. This will help you calculate how much Ca2+ you need in 1 mL per 1 mg increase.
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LyreTail

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Re: Help Calculate a Dilution of Calcium Chloride
« Reply #2 on: December 02, 2007, 03:46:08 PM »

Yes.
10 gallon [US, liquid] = 37.85 liters

CaCl2+H4O2 = CaCl2+2H20

147.0146 Molecular weight ( g/mol)
73.5073 Equivalent weight ( g/mol)

Breakdown weight and Mole percentages
Ca  /  Wt = 27.3%   /  Mole = 11.1%
Cl   /  Wt = 48.2%   /  Mole = 22.2%
H    /  Wt = 2.7%    /  Mole= 44.4%
O    /  Wt = 21.8%   /  Mole = 22.2%

I want to find out how much of this compound to add to a single liter of water in order to make a dilution of 1 ml of dilution into 37.85 liters of water = 1 mg/l increase in Ca ( Calcium )

I really do not have a chemistry background so I am a little confused about what to do with all the information this calculator above gave me but I thought posting it may aid others. I also do not have a scale to measure grams to figure out how many grams are in a tsp of CaCl2+2H20
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Borek

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Re: Help Calculate a Dilution of Calcium Chloride
« Reply #3 on: December 02, 2007, 09:49:48 PM »

To get 1 mg of Ca2+ per 1L after diluting in 10 gallons you must have 37.85 mg of calcium per 1 mL of the solution added - sounds OK?

Now, you know there is 0.273 g of Ca per 1 g of CaCl2.2H2O - it is in the numbers you posted.

Calculate how much CaCl2.2H2O must be added to every 1 mL of solution to get 37.85 calcium per mL, multiply by 1000 for 1 L and divide by the mass of calcium chloride per tablespoon (no idea).
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LyreTail

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Re: Help Calculate a Dilution of Calcium Chloride
« Reply #4 on: December 03, 2007, 04:18:42 PM »

A 1% solution is equal to 10 g dissolved in 1 liter of solvent.
1 milligram = 0.001 grams

So I am looking for a solution of 37,850 mg of Ca into 1 liter of water
or  (37,850 *.727)+37,850 = 65366.95 mg of CaCl2+2H2O
or a total of 65.37 grams of calcium Chloride Dihydrate into 1 liter of water

Does that look correct so far?


If so then I just need to know how much a level tsp of CaCl2+2H2O weighs?
I thought perhaps the molar weight numbers would help predict the volume but this is where my chem knowledge breaks down.

Most chemicals like this weigh between 5 and 7 grams ( I use several fertilizers in my aquarium such as K2SO4, KNO3 and KH2PO4 and all these are in this range but I do not know the weight of calcium chloride dihydrate)
--------------------------------------------------------------------
I found this on an MSDS sheet
Specific Gravity: Bulk density: 0.835 (Water = 1)
  I do not know what to do with this info

this on a different spec sheet
Density: 1.85g/cm3(20ºC)
1.85 gram/cubic centimeter = 1.85 gram/milliliter
5 ml in a metric tsp ( 5 cubic centimeters) = 9.25 grams per tsp
65.37 / 9.25 = a total of 7 tsps of Calcium Chloride Dihydrate into 1 liter of water = the concentration I was looking for

This answer of 7 tsps seems too low. Perhaps I did something wrong in the math or made a wrong assumption?

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Borek

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Re: Help Calculate a Dilution of Calcium Chloride
« Reply #5 on: December 03, 2007, 09:43:26 PM »

(37,850 *.727)+37,850 = 65366.95 mg of CaCl2+2H2O
or a total of 65.37 grams of calcium Chloride Dihydrate into 1 liter of water

Something is wrong here. (37,850 *.727)+37,850 part doesn't make sense. You know calcium is 0.273 (27.3%) of the salt mass, so you need 37,850/0.273 = 138,645 mg or 138 g.

Quote
If so then I just need to know how much a level tsp of CaCl2+2H2O weighs?

Yes.

Quote
I thought perhaps the molar weight numbers would help predict the volume

Unfortunately - no way. Tables and MSDS.

Quote
I found this on an MSDS sheet
Specific Gravity: Bulk density: 0.835 (Water = 1)
  I do not know what to do with this info

0.835 g/mL - bulk density is also called "apparent powder density", it takes air between crystals into consideration.

Quote
Density: 1.85g/cm3(20ºC)
1.85 gram/cubic centimeter = 1.85 gram/milliliter
5 ml in a metric tsp ( 5 cubic centimeters) = 9.25 grams per tsp

No idea what density it refers to. Could be it is the density of the crystal itself, if so, using it leads nowhere (your solution will be diluted much more then you think).
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LyreTail

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Re: Help Calculate a Dilution of Calcium Chloride
« Reply #6 on: December 05, 2007, 05:26:02 PM »

I was trying to find the number of the other 72% of non Ca ingredients and then add the Ca amount back into it.
Now that I look at it, it does not make sense to me either.

so I want 37,850 mg of Ca into 1 liter of water
I need to find out the total amount of CaCl2+2H20 to add to the 1 liter bottle
So I will set up the Law of Porportions

37,850 mg     total mg
-------     X  --------
  27.3%          100%
Ok - I see your answer now
(37,850 x 100)/ 27.3 = 138645 mg
138645 mg = 138.645 g

Your answer reverse checks - Thanks.
138.645 * 27.3% = 37.85 grams

I guess I will have to buy a scale
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Borek

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Re: Help Calculate a Dilution of Calcium Chloride
« Reply #7 on: December 05, 2007, 08:47:33 PM »

Your answer reverse checks - Thanks.

It is always good idea to check numbers by yourself :)

Quote
I guess I will have to buy a scale

Most likely any kitchen scale will do, you need around 140 g.

Note: take care of your CaCl2. It is hygroscopic and will have tendency to get more water, in effect your solutions will be less concentrated then you need. Keep it tightly closed all the time and open for as short as possible.
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