What happens to Cl and Cl2?

[Psymon]

Dear Reef2Reef Chemistry Pros,

I am looking to make some of my own trace elements. I found some threads and bought the respective chemicals online.

There are two things I don't understand:

1. Why can't one buy the pure form of the chemicals as a liquid?
eg Potassium, Iodine, Manganese etc...

2. What happens to the other elements when I mix the following with H2o?

ZnCl2 - Zinc Chloride
KI - Potassium Iodide
MnCl2 - Manganese(II) chloride tetrahydrate
KCl - Potassium Chloride

Where does the Cl + Cl2 go during/after the reaction with H2o? Does that get dosed into the reef? Isn't that dangerous?


Here are the quotes, and directions I am going to use for the elements (compounds? [because they are combined - whats the right term?]) I bought.
If someone could confirm they are correct, that would help a lot!

https://www.reef2reef.com/threads/diy-potassium.278160/#post-3370334

Potassium chloride has a solubility of 34.2 g / 100 mL of water @ 20 C, so our solution must be less concentrated than that. Let's choose an arbitrary concentration of approximately half that by dissolving 150 grams of KCl in enough water to make up a total volume of 1000 mL. Since the Molecular Mass of KCl is 74.55, that gives a molarity of 150 / 74.55 = 2.012M in our solution. Since the Atomic Weight of potassium is 39.0983, then each mL of our solution will contain 2.012 * 39.0983 = 78.67 mg of potassium. In order to raise the potassium level of 100 gallons of water by 10 PPM, we need to add 10 * 100 * 3.7854 = 3785.4 mg of potassium. So, it will take 3785.4 / 78.67 = 48.12 mL of our 150g / 1000 mL KCl solution to accomplish this. For your 127 gallons, you would need 48.12 * 127 / 100 = 61.11 mL of our solution. This is assuming your KCL is 100% pure; your MSDS indicates a slightly lower concentration of KCl in the substance you are using. Adjust the numbers above accordingly, if you wish.

https://www.reef2reef.com/threads/post-your-diy-additives-here.344149/page-3#post-4558264

https://www.convertunits.com/
e.g. potassium iodide = 76.4% iodide. 1l stock with 1gr potassium iodide = 764 ppm iodide. 1ml = +0.76 ppm per liter aquariumwater. if you have 100l tank and want to raise by 0.01 you need 1.31ml. (0.0076 ppm / 0.01 ppm ). good luck!

https://www.reef2reef.com/threads/diy-zinc-solution.374652/#post-4620982

Zinc chloride is 48.6 zinc by weight.

500 grams thus contains 240 grams of zinc.

If you dissolve that in RO/DI until you get to 1 L of total volume, then each 1 mL will contain 1/1000 of that amount, or 240 mg zinc per mL.

You are going to need a much more dilute solution for dosing.

Do you have a scale to weigh out a portion of the 500 g, or do you want to di it by diluting the solution above again?

Assuming the latter, take 1 mL of the solution (240 mg of zinc) and dissolve it in 1 L total RO/Di water, to give a concentration of 0.24 mg/mL (240 ug/mL).

The total NSW level of zinc is about 6 ug/L in seawater, so if you add 1 mL of this second solution (240 ug) to 40 Liters of seawater, you will add the full NSW level of zinc, 6 ug/L (which may be way more than you'd want to dose, unless the level is zero).

https://www.reef2reef.com/threads/post-your-diy-additives-here.344149/page-4#post-5145534

/// what I found so far ///
Manganese(II) chloride tetrahydrate is 28% manganese by weight.
Dissolve 1 gram in 100o mL (grams) fresh water. Manganese = 280 ppm.
Take 1 mL (1 g) of that mix and dissolve in 1000 mL of fresh water. Mn = 0.28 ppm (=280 ug/L).
Add 1 mL of that to 100 mL of fresh water. Mn = 2.8 ug/L
Add 13.5 mL of that to 100 gallons of tank water. Conc boost to tank = 0.1 ug/L Mn
...

-----

 

[sghera64]

How is it that you feel you need to add these trace elements? Perhaps you got results from and ICP-OES test.

No shame, but it appears that you might not be very familiar with solving chemistry problems. If that is the case, I wonder if you have ruled out correcting any problematic trace element deficiencies with pre-made products, or simply doing water changes. For small differences, water changes are probably the safest (and perhaps cheaper if you factor in the cost of killing a lot of coral due to a miscalculation).

To answer your question though, you need to understand the Cl- is chloride ion and is a major component of sea water. Cl2 (written as such) denotes a molecule of pure chlorine gas; a very strong oxidizer which reacts with water for form hydrochloric acid and is lethal at relatively small doses. You are not working with Cl2 in an of your examples. ZnCl2 represents a salt made from Zn+2 atom and two Cl- atoms. Likewise MnCl2 is one molecule of Manganese with an oxidation state of +2 ionically bonded to two chloride (-1 oxidation state) atoms. When these are dissolved in pure water, they "dissociate" into their respective ions. Meaning, you have Zn+2, Mn+2 and chloride ions surrounded by and moving amongst the water molecules.

Unless your sources are providing you with specific dosing calculators, the next set of questions you will need to answer is how much of each chemical (e.g. ZnCl2, KI) to add to how much water to make a solution of a specific concentration. Then you will need to know how much of each of these to add to close a specific deficiency. This is why it is best to:

1. Ensure the deficiency in trace elements is significant enough that A.) it must be resolved and 2.) it cannot easily be remedied with water changes.

2. Use premixed trace element additives that have these elements in them. Chances are if you are lacking Zn, you are lacking other elements that come together in a bottle. See Red Sea trace elements or even Triton's elements.

 

[Psymon]

How is it that you feel you need to add these trace elements? Perhaps you got results from and ICP-OES test.

No shame, but it appears that you might not be very familiar with solving chemistry problems. If that is the case, I wonder if you have ruled out correcting any problematic trace element deficiencies with pre-made products, or simply doing water changes. For small differences, water changes are probably the safest (and perhaps cheaper if you factor in the cost of killing a lot of coral due to a miscalculation).

To answer your question though, you need to understand the Cl- is chloride ion and is a major component of sea water. Cl2 (written as such) denotes a molecule of pure chlorine gas; a very strong oxidizer which reacts with water for form hydrochloric acid and is lethal at relatively small doses. You are not working with Cl2 in an of your examples. ZnCl2 represents a salt made from Zn+2 atom and two Cl- atoms. Likewise MnCl2 is one molecule of Manganese with an oxidation state of +2 ionically bonded to two chloride (-1 oxidation state) atoms. When these are dissolved in pure water, they "dissociate" into their respective ions. Meaning, you have Zn+2, Mn+2 and chloride ions surrounded by and moving amongst the water molecules.

Unless your sources are providing you with specific dosing calculators, the next set of questions you will need to answer is how much of each chemical (e.g. ZnCl2, KI) to add to how much water to make a solution of a specific concentration. Then you will need to know how much of each of these to add to close a specific deficiency. This is why it is best to:

1. Ensure the deficiency in trace elements is significant enough that A.) it must be resolved and 2.) it cannot easily be remedied with water changes.

2. Use premixed trace element additives that have these elements in them. Chances are if you are lacking Zn, you are lacking other elements that come together in a bottle. See Red Sea trace elements or even Triton's elements.

Hi sghera64, thanks for your reply.
Yes, I should mention it's for ICP-OES tests. (Triton)

Thank you for the explanation. I didn't pay enough attention in Chemistry @ school (now I wish I had)...
So chloride ions are essentially harmless in the reef tank (as there is a massive amount of these in saltwater already)? Do chloride ions then increase/affect salinity?

1. Triton recommends daily dosing of Mn, Zn, I, and Va. I would like to do that. I ran the costs of doing that over a year and the price was high enough for me to consider an alternative. Then I remember reading something on R2R about DIY trace elements and scoured all the information together (see OP and links).
2. hmmm, I agree. I liked the idea of DIY (and avoiding some reef tax) and learning some chemistry at the same time.

 

[sghera64]

Not to worry about your chemistry expertise. Most reefers do not claim chemistry as a strong suite and there are more than enough folks on R2R to make up for it. Plus, you've posted your question in the right forum.

Chloride is a major contributor to salinity, along with sodium, magnesium, calcium, sulfate, bicarbonate and many more dissolved solids. Since you asked, you might want to know that adding home-made salts comes with risk of skewing the balance of salinity. For example if you always added chloride salts to adjust Magnesium and Calcium, your system would accumulate chloride and decrease the ratio of sulfate. Some use a balanced approach to manage this (e.g. MgCl2 + MgSO4), while most simply do a periodic (say annual) major water change. A major water change might mean doing 3x 30-40% water changes over a couple of weeks. This sort of "resets" the ratios if you are using a fully balanced salt.

I won't knock Triton's approach or their ability to illustrate how far away your tank water is from sea water. However, just because there is a difference, does not mean you have to respond / treat it. For a plethora of understandable articles on reef chemistry Google Randy Holmes-Farley and Reef Chemistry. Here is a sample: [LINK].

Are you using the Triton Method?

Do you have a macro algae refugium?

Given the elements you are seeking to treat, the only one I would be concerned with is Mn and only if you are having a hard time growing macro algae when you also have high NO3 and higher PO4. If you are low on Mn (manganese), then you are likely low on iron too.

For iodine as well as Iron and Mn, there are some rather affordable alternatives. One example is Kent Marine. You can buy a bottle of iron + manganese on Amazon for a pretty low cost. These come with some general dosing guidance, which I would follow for 3 months before re-submitting a sample for ICP-OES analysis. All else being relatively the same in your system, you can then make a proportional adjustment based on the impact your additions had to the numbers.

BRS just did a short video summary of this and concluded for their purposes, they find it better just to go with regular water changes. The cost of monthly ICP-OES + trace element additions + the occasional major water change outweighed the cost and simplicity of regular smaller water changes [But remember, they make money selling us salt ].

I'm hoping a few others will chime in here an maybe provide some alternative ways to approach your situation.

Happy Reefing!

 

[Dkeller_nc]

While I personally agree with sghera64 in that I'd use an all-in-one trace element supplement if I felt I needed it, you might choose to post the actual amounts and compounds that you intend to dissolve together to make your own, or are we misunderstanding and you intend to make 4 separate solutions?

One other detail -some of these compounds exist in hydrated form - zinc chloride, for example, can exist as a hydrates of 1, 1.5, 2.5, 3 and 4 water molecules per ZnCl2 molecule. It would be important to know if you have the anydrous form of your chemicals, or if they're one of the various hydrates, since that will affect the calculated quantity required to get a particular molar concentration in your solution.

 

[Psymon]

Not to worry about your chemistry expertise. Most reefers do not claim chemistry as a strong suite and there are more than enough folks on R2R to make up for it. Plus, you've posted your question in the right forum.

Chloride is a major contributor to salinity, along with sodium, magnesium, calcium, sulfate, bicarbonate and many more dissolved solids. Since you asked, you might want to know that adding home-made salts comes with risk of skewing the balance of salinity. For example if you always added chloride salts to adjust Magnesium and Calcium, your system would accumulate chloride and decrease the ratio of sulfate. Some use a balanced approach to manage this (e.g. MgCl2 + MgSO4), while most simply do a periodic (say annual) major water change. A major water change might mean doing 3x 30-40% water changes over a couple of weeks. This sort of "resets" the ratios if you are using a fully balanced salt.

I won't knock Triton's approach or their ability to illustrate how far away your tank water is from sea water. However, just because there is a difference, does not mean you have to respond / treat it. For a plethora of understandable articles on reef chemistry Google Randy Holmes-Farley and Reef Chemistry. Here is a sample: [LINK].

Are you using the Triton Method?

Do you have a macro algae refugium?

Given the elements you are seeking to treat, the only one I would be concerned with is Mn and only if you are having a hard time growing macro algae when you also have high NO3 and higher PO4. If you are low on Mn (manganese), then you are likely low on iron too.

For iodine as well as Iron and Mn, there are some rather affordable alternatives. One example is Kent Marine. You can buy a bottle of iron + manganese on Amazon for a pretty low cost. These come with some general dosing guidance, which I would follow for 3 months before re-submitting a sample for ICP-OES analysis. All else being relatively the same in your system, you can then make a proportional adjustment based on the impact your additions had to the numbers.

BRS just did a short video summary of this and concluded for their purposes, they find it better just to go with regular water changes. The cost of monthly ICP-OES + trace element additions + the occasional major water change outweighed the cost and simplicity of regular smaller water changes [But remember, they make money selling us salt ].

I'm hoping a few others will chime in here an maybe provide some alternative ways to approach your situation.

Happy Reefing!

Thanks for your reply.

I am using the Triton method.
I have a Macro algae refugium.

The refugium does just ok. No issues there.