Purpose of sodium carbonate?

[snakeblitz33]

I use sodium bicarbonate (baking soda) to increase alkalinity occasionally. But what about sodium carbonate? What does it do in a reef? Is it a pH upper or downer? Is there any benefit of blending the two?
Anyone?
I can buy sodium carbonate at a local pool cleaning store for cheap.

 

[geoj]

I use sodium bicarbonate (baking soda) to increase alkalinity occasionally. But what about sodium carbonate? What does it do in a reef? Is it a pH upper or downer? Is there any benefit of blending the two?
Anyone?
I can buy sodium carbonate at a local pool cleaning store for cheap.
Most bake, sodium bicarbonate to make sodium carbonate. So it really does not mater I stopped use of sodium bicarbonate many years ago so I don't remember the difference from sodium carbonate. I have always liked Seachems reef builder and buffer as a way to raise alk because they are blends. Sodium bicarbonate and sodium carbonate will change pH, but only temporarily so I would use it for alk and not pH.

 

[snakeblitz33]

So baked baking soda is sodium carbonate? By baking it, you drive off the carbon dioxide i know - so i guess that makes it become carbonate. Wow. I didnt realize.
I

 

[snakeblitz33]

So sodium carbonate raises pH and sodium bicarbonate lowers pH. They both raise alkalinity. So, what happens if you mix the two in equal portions? Would you get a zero pH effect while still raising alkalinity?

 

[bang guy]

Yes, mixing will cancel out the PH change depending on how much of each.
Most of the PH rise from adding Sodium carbonate is temporary, and all of the PH drop from adding Sodium bicarbonate is temporary.

 

[snakeblitz33]

So in synthetic salt mixes, do they typically use sodium bicarbonate to keep costs low? Since it is temporary,... Is that one reason to age new salt water?

 

[bang guy]

Quote:
Originally Posted by SnakeBlitz33 http:///t/391870/purpose-of-sodium-carbonate#post_3477250
So in synthetic salt mixes, do they typically use sodium bicarbonate to keep costs low? Since it is temporary,... Is that one reason to age new salt water?
They also use Sodium carbonate and some Sodium borate for Alkalinity. Yes, this is absolutely one of the reasons new saltwater should be agitated for a while before using it.
The ratio of Carbonate to Bicarbonate fluctuates depending primarily on PH so it can take some time for the levels to get to a stable state. Agitating, or even aerating, the water can help a lot to ensure that none of the dissolved gasses can either becompe depleted nor overabundant.
Let's say for demonstration purposes that the ratio of Carbonate to Bicarbonate is 1 to 14 (approximate). When PH drops the Carbonate will tend to grab Carbonic Acid (CO2) and convert to Bicarbonate. As we know, when acid is removed the PH rises. The effect is that the drop in PH is buffered.
Back to Carbonates effect on PH. If you add a teaspoon of Sodium carbonate to the water most of that carbonate will tend to consume CO2 to form Bicarbonate in order to maintain the Carbonate/Bicarbonate ratio of 1:14. It is this consumption of CO2 that is responsible for most of the PH rise. The reason it is temporary is because the CO2 levels will rise to former levels fairly quickly through gas exchange at the water surface. This is why adding a "buffer" doesn't "fix" low PH unless alkalinity was actually low.
The opposite is also true so if you add a teaspoon of Sodium bicarbonate to the water some of the Bicarbonate will give up CO2 in order to maintain the Carbonate/Bicarbonate ratio. This will lower the PH because there is now more CO2 in the water. As the CO2 dissipates through gas exchange the PH rises back to normal. So, since the ratio is about 1:14 not very much Bicarbonate releases CO2 so there really isn't much of a PH drop.

 

[snakeblitz33]

Thank you for explaining that in more detail Guy. I appreciate it.
So, it really doesn't matter if your mix the two or not for a neutral pH swing - it's temporary. You just have to know if your pH is low or high... then if you know that, you know which alkalinity additive to use.

 

[bang guy]

Quote:
Originally Posted by SnakeBlitz33 http:///t/391870/purpose-of-sodium-carbonate#post_3477267
Thank you for explaining that in more detail Guy. I appreciate it.
So, it really doesn't matter if your mix the two or not for a neutral pH swing - it's temporary. You just have to know if your pH is low or high... then if you know that, you know which alkalinity additive to use.
I typically advise Sodium bicarbonate over Carbonate for two reasons: Sodium bicarbonate is cheaper and the PH fluctuation is less. But to be honest, a 1:14 ratio of Sodium carbonate to Sodium bicarbonate with a pinch of Sodium borate would be a much better additive for Alkalinity.

 

[snakeblitz33]

Quote:
Originally Posted by Bang Guy http:///t/391870/purpose-of-sodium-carbonate#post_3477274
I typically advise Sodium bicarbonate over Carbonate for two reasons: Sodium bicarbonate is cheaper and the PH fluctuation is less. But to be honest, a 1:14 ratio of Sodium carbonate to Sodium bicarbonate with a pinch of Sodium borate would be a much better additive for Alkalinity.
Sounds simple - why can't I find this kind of additive already on the market then?
How likely is it that one could make their own customized synthetic sea salts in bulk?? I know Garry Elliot at Saltwater Correct makes his own to sell...

 

[bang guy]

Quote:
Originally Posted by SnakeBlitz33 http:///t/391870/purpose-of-sodium-carbonate#post_3477278
Sounds simple - why can't I find this kind of additive already on the market then?
A lot of the commercial Alkalinity additives are similar.
Quote:
How likely is it that one could make their own customized synthetic sea salts in bulk?? I know Garry Elliot at Saltwater Correct makes his own to sell...
If you were to make a couple tons at a time you could do it. It's just that in small batches it would be really expensive.

 

[snakeblitz33]

Quote:
Originally Posted by Bang Guy http:///t/391870/purpose-of-sodium-carbonate#post_3477280
A lot of the commercial Alkalinity additives are similar.
If you were to make a couple tons at a time you could do it. It's just that in small batches it would be really expensive.
Not really from what I am looking at so far...
You would have to buy all of the materials in bulk, yes. But, you could make small batches out of your bulk supplies...
If you had a lot of water to change or made it a small business venture I guess it would be worth it - but to make as much salt mix as what a typical hobbyists needs, I wouldn't think it would be cost effective.

 

[geoj]

Thank you for explaining that in more detail Guy. I appreciate it.
So, it really doesn't matter if your mix the two or not for a neutral pH swing - it's temporary. You just have to know if your pH is low or high... then if you know that, you know which alkalinity additive to use.
So you can see now why I don't use it to adjust pH. After a few hours the pH will swing back. I would use it for adjusting alk only. If you did keep throwing it in to adjust pH you would over shoot your alk target and run out of room to keep pH up.

 

[snakeblitz33]

No, i understand that completely. I know that pH buffers dont fix pH, they just temporarily make it rise or fall. I just didnt know which did what. Now i know that sodium carbonate is nothing more than baked sodium bicarbonate.