Sorry for the delay on this 
First and foremost there are some things that you will need and some calculations that you may need to do.
1) A gram scale is a must if you are to have any accuracy. The more decimal places the better. .01 is the minimum I would recomend to anyone for any of the test kit verifications that I will post. If you have a .001 or better then outstanding! I will post all results to .001.
2) Some kind of volumetric measuring device. A 1L graduated cylinder with 1mL markings would be the best.
3) A calcium source that will be almost certainly bromine free. The reason for the lack of bromine is that the atomic weight of Br is heavier than that of Cl. Aside from that Br is not safe to be adding to a reef tank, as the evidence that its removal is not fast enough and will build up and cause issues. But for now try to get the purest CaCl2 that you can get. Maybe at some point in time we can get into purifying CaCl2 that is tainted with Br. But the process is dangerous and not for eveeryone so I highly doubt I will cover it.
4) An Oven ... Well you do need one for the Ca test kit. :neutral:
OK first steps are to know exactly what we are testing for! So Calcium ... Great! But guess what in colums in the periodic table have (commonly) the same valance charge, or more importantly is that they form similar bonds. Like CaCl2 and CaBr2. Right below Cl on the periodic table is Br. The reason for knowing this is that you should realize that if you look at Ca on the periodic table the element directly above it is Mg. So this is important because test kits are usually used to test for both with one minor variation to "filter" out the ion we do not want to test for nor do we want it to interfere with the test kit.
The most common form of Ca and Mg testing is done with a few chemicals, but from different manufacturers you will get different reagents. The ones that I am most familiar with utilizes: Murexide (ammonium purpurate), Sodium Hydroxide (Lye, NaOH) , EDTA (ethylenediaminetetraacetic acid).
Here is how the "murexide" test works:
Murexide is a color indicator for calcium as long as the pH is above 11.
NaOH is added to allow the pH to be so high but it also has another added bonus. Mg in solution is mostly precipitated as its most insoluble Hydroxide (same as Calcium Hydroxide with regards to the very low solubility).
The third part is EDTA it is simply a chelating agent, and for the basis of this post not much more is needed to know. The chelating agent basically surrounds the Ca++ Ion and makes it almost disappear to the test kit. Think about the EDTA as little trash bags that surround the Ca++ Ion but they are still in solution but not able to be seen by the test kit.
Here is how to make the sample to test your Ca test kit:
1) exactly 1L of water. If you have a 1L beaker look up the work miniscus. If you do not have beaker but have a gram scale with more than 1,000 g capability with .01 resolution than tare out the container then weigh 1,000.00g of water.
2) get some Anhydrous Calcium Chloride. Anhydrous means no water. The CaCl2 will absorb water from the atmosphere so you must bake it to drive off any water that it has absorbed. 400F spread very thin for 30 minutes should do the trick!
3)The Math (I've done it for you ) note that 1ppm = 1mg/L and 1 mg = .001 g
420 mg Ca .......110.9 g CaCl
------------ x -------------- = 1164.45mg CaCl2 = 420 ppm Ca++
1L ......................40g Ca
So really you need 1.164g in 1 L of PURE water. This mixture will give you 420ppm Ca++.
Good Luck
Feed back is always welcome.
First and foremost there are some things that you will need and some calculations that you may need to do.
1) A gram scale is a must if you are to have any accuracy. The more decimal places the better. .01 is the minimum I would recomend to anyone for any of the test kit verifications that I will post. If you have a .001 or better then outstanding! I will post all results to .001.
2) Some kind of volumetric measuring device. A 1L graduated cylinder with 1mL markings would be the best.
3) A calcium source that will be almost certainly bromine free. The reason for the lack of bromine is that the atomic weight of Br is heavier than that of Cl. Aside from that Br is not safe to be adding to a reef tank, as the evidence that its removal is not fast enough and will build up and cause issues. But for now try to get the purest CaCl2 that you can get. Maybe at some point in time we can get into purifying CaCl2 that is tainted with Br. But the process is dangerous and not for eveeryone so I highly doubt I will cover it.
4) An Oven ... Well you do need one for the Ca test kit. :neutral:
OK first steps are to know exactly what we are testing for! So Calcium ... Great! But guess what in colums in the periodic table have (commonly) the same valance charge, or more importantly is that they form similar bonds. Like CaCl2 and CaBr2. Right below Cl on the periodic table is Br. The reason for knowing this is that you should realize that if you look at Ca on the periodic table the element directly above it is Mg. So this is important because test kits are usually used to test for both with one minor variation to "filter" out the ion we do not want to test for nor do we want it to interfere with the test kit.
The most common form of Ca and Mg testing is done with a few chemicals, but from different manufacturers you will get different reagents. The ones that I am most familiar with utilizes: Murexide (ammonium purpurate), Sodium Hydroxide (Lye, NaOH) , EDTA (ethylenediaminetetraacetic acid).
Here is how the "murexide" test works:
Murexide is a color indicator for calcium as long as the pH is above 11.
NaOH is added to allow the pH to be so high but it also has another added bonus. Mg in solution is mostly precipitated as its most insoluble Hydroxide (same as Calcium Hydroxide with regards to the very low solubility).
The third part is EDTA it is simply a chelating agent, and for the basis of this post not much more is needed to know. The chelating agent basically surrounds the Ca++ Ion and makes it almost disappear to the test kit. Think about the EDTA as little trash bags that surround the Ca++ Ion but they are still in solution but not able to be seen by the test kit.
Here is how to make the sample to test your Ca test kit:
1) exactly 1L of water. If you have a 1L beaker look up the work miniscus. If you do not have beaker but have a gram scale with more than 1,000 g capability with .01 resolution than tare out the container then weigh 1,000.00g of water.
2) get some Anhydrous Calcium Chloride. Anhydrous means no water. The CaCl2 will absorb water from the atmosphere so you must bake it to drive off any water that it has absorbed. 400F spread very thin for 30 minutes should do the trick!
3)The Math (I've done it for you
) note that 1ppm = 1mg/L and 1 mg = .001 g420 mg Ca .......110.9 g CaCl
------------ x -------------- = 1164.45mg CaCl2 = 420 ppm Ca++
1L ......................40g Ca
So really you need 1.164g in 1 L of PURE water. This mixture will give you 420ppm Ca++.
Good Luck
Feed back is always welcome.
