Two-Part Calcium and Alkalinity Supplement System - talk

[Russ Braaten]

First, Here is the URL for the Two-Part Calcium and Alkalinity Supplement System

http://reefkeeping.com/issues/2006-02/rhf/index.php

I have made this stuff two times and thought a lot about the procedure between the two times. The Calcium part goes together great but the Alkaline part will not stay in solution at the amounts prescribed. The bottle of the Alkaline solution had chunks of sediment at the bottom. I even emailed the creator, Randy Holmes-Farley, about the problem of the sediment. His answer was to heat up the water more and to cook the baking soda more to get more of the water out of it.

The second time I made it I cooked the baking soda long enough and mixed it long enough to get all the water out of it. I did heat the water in a huge pot and was able to dissolve all the baking soda into the water and the water looked perfectly clear.

There is a problem that I learned about in 6th grade Chemistry. Solutions will mix only until they become saturated. Also the saturation point goes up with heat and once cooled the over saturated chemical will fall out of the solution and often form crystals.

This is what happened. (Now I am getting to the point of the post) Once the solution started to cool it formed crystals on the sides and bottom of the pot. Mr Holmes-Farleys alkaline solution is just too strong to stay in solution. Shaking it before adding it to the tank does little to get the sediment mixed in.

What I did was to let the pot of solution to cool down and have the extra chemicals crystalize out and turn into sediment. I then siphoned the clear liquid through a foam filter and into my 5 gallon containers. It has been a few days now and there is no percipatate at the bottom of the jug.

My conclusion: Randy Holmes-Farley's Alkalinity Supplement is way too strong to stay in solution and leaving crystals at the bottom of your jug is dangerous in that you may over-dose your tank if you let the sediment get into your tank.

 

[pwhitby]

i have made it many times and not experienced that Russ.

What you are discussing is supersaturation, which is quite easy to deal with. Instead of making it up in 1gallon, make both up in 2 gallons. Problem solved.

Randy is correct about heating the alkalinity part first. Bake it for several hours and it will go into solution very easily. I add the hot powder to cold water and it does just fine.

Paul.

 

[ReeferRyan]

I know we have scientists here, so please correct me if I am wrong, but I think I remember from Chemistry that pure water reacts differently than a solution. I know it messes with the boiling/freezing point but what about the solubility? My point is maybe the water you are using has too many other things already dissolved in it and that is messing with its ability to saturate properly. Are you using purified water Russ?

 

[papagimp]

I've used ro/di and have had similar problems getting the baking soda to dissolve.

 

[captbunzo]

I have had quite a bit of success with Randy's 2 part supplement (which is really a 3 part supplement once you add the magnesium supplement in there).

 

[TimV]

To answer your question, it really depends on what you're trying to dissolve in that water. Some materials will need anions or cations that might be present in dirtier water.

In this particular case, the recipe calls for you to essential dissolve the baking soda at about 2x its solubility in water. Baking it drives off CO2 and H2O and converts the bicarbonate to carbonate, increasing its solubility (the latter is more than 3x more soluble). So you might get it into solution, especially with enough baking to drive off enough CO2, but that solution will begin to reabsorb CO2 from the atmosphere and sodium bicarbonate will fall out of solution.

You can skip the whole baking step by using sodium carbonate in the first place, but sodium bicarbonate will still precipitate as CO2 is absorbed over time.

T

 

[papagimp]

Can we just use half the required baking soda and use twice the dosage with our tank?

 

[TimV]

<a href=showthread.php?s=&postid=8744791#post8744791 target=_blank>Originally posted</a> by papagimp
Can we just use half the required baking soda and use twice the dosage with our tank?

Yes, and no.

If you don't bake it, you'll be adding sodium bicarbonate rather than sodium carbonate to your tank. That will drive your pH downward. If you don't have pH problems, you are fine.

Ultimately, the best bet is to go ahead a bake your baking soda, for several hours if necessary. Don't make too much at one time, or aliquot it into smaller, well-sealed containers to prevent CO2 absorption.

T

 

[Russ Braaten]

Tim, I had no idea that baking actually changed the bicarbonate to carbonate. I did cook the bicarbonate for 2 hours at 400 degrees. I did not stir though. I did notice that I had a lot of gas boil off when I was mixing and heating it. Does that tell me anything?

Paul, are you saying to do what Adam asked? Basically make a 50% solution?

 

[TimV]

<a href=showthread.php?s=&postid=8746936#post8746936 target=_blank>Originally posted</a> by Russ Braaten
Tim, I had no idea that baking actually changed the bicarbonate to carbonate. I did cook the bicarbonate for 2 hours at 400 degrees. I did not stir though. I did notice that I had a lot of gas boil off when I was mixing and heating it. Does that tell me anything?

Paul, are you saying to do what Adam asked? Basically make a 50% solution?

If you make a 50% solution and don't still bake it, you may have pH problems if your pH is borderline.

If you look at Randy's recipes, you'll see one that was half strength and no baking. That amount of baking soda is exactly the saturation point in 1 gallon of water.

Bake the bicarb for longer and stir it. When Paul and I bake it, we'll do it for 4 or 5 hours. Alternatively, spread it out in a much thinner layer.

You can also see if you can buy soda ash somewhere instead. That way you've got the carbonate right there.

T

 

[TimV]

<a href=showthread.php?s=&postid=8746936#post8746936 target=_blank>Originally posted</a> by Russ Braaten
Tim, I had no idea that baking actually changed the bicarbonate to carbonate. I did cook the bicarbonate for 2 hours at 400 degrees. I did not stir though. I did notice that I had a lot of gas boil off when I was mixing and heating it. Does that tell me anything?

Paul, are you saying to do what Adam asked? Basically make a 50% solution?

I forgot to mention what you are doing when you bake it. The reaction is (if memory serves) 2 NaHCO3 -> Na2CO3 + H2O +CO2

I looked up sources of soda ash for you. Apparently, you can buy pure sodium carbonate at pool stores under a brand called pH UP. Keep it well sealed though as it will absorb H20 from the air. If someone is serious about soda ash, I'll check my math to figure out how much to add.

T