Sodium Hydroxide

[recife111]

Has anyone dose sodium hydroxide to raise KH.
Sodium hydroxide is far more concentrated so very little is required, what is the downside?

[Randy Holmes-Farley]

It is like adding limewater: it boosts pH a lot. About 0.6 to 0.7 pH units instantly for a 0.5 meq/L (1.4 dKH) boost to alkalinity. So slow addition is necessary.

Aside from that, the only drawback is that it adds no calcium, and does not supply any ions aside from sodium so over time might boost sodium relative to other ions, such as magnesium, potassium, etc. Those problems are eliminated by using limewater or two part additives rather than sodium hydroxide.

[recife111]

Randy would it not increase carbonate ?
I was looking to add it with a Peristaltic pump running 24/7. dosing about 200ml a day.

Could i mix it with the sodium bicarb?

[Randy Holmes-Farley]

It will boost alkalinity, just as limewater does, and that ultimately raises all of bicarbonate, carbonate, and OH-.

It first adds OH- (hydroxide), which when added converts some bicarbonate into carbonate:

OH- + HCO3- ---> CO3--

The pH is then raised , and the tank pulls in CO2 from the air, converting some of that extra carbonate back into two bicarbonates:

CO3-- + CO2 + H2O ---> 2HCO3-

[recife111]

So what would happen if i added a little sodium hydoxid to sodium bicarb?

[Randy Holmes-Farley]

You'd make sodum carbonate.

NaOH + NaHCO3 ---> Na2CO3 + H2O

[Boomer]

Meaning, recife that if you made a concentrated solution of......

NaOH + NaHCO3 ---> Na2CO3 + H2O

.....crystals of Na2CO3 would form, which could be filtered out and dried. If you just mixed some dry NaOH + NaHCO3 not much of anything is going to happen. However, if these dry substances where added to water you may get some of this

NaOH + NaHCO3 ---> Na2CO3(s) + H2O

But this when diluted as it enters the tank would be as Randy showed above

OH- + HCO3- ---> CO3--

or

Na2CO3(s) ---> 2Na+ + CO3--( in solution raising the Alk and pH)

[Acromaniac]

Sorry to bring up an old thread, but how much will x amount of sodium hydroxide raise the ALK and PH by?

Thanks

[bertoni]

It's going to be about twice as concentrated as sodium carbonate, per unit weight, in terms of alkalinity. What do you have for measuring equipment? If you don't have a scale, my first guess would be to use half the amount recommended for sodium carbonate, at most. For pH, it's going to have a strong effect, similar to Kalk.

I would avoid using lye. The solution is fairly corrosive.

[disc1]

Originally Posted by Acromaniac

Sorry to bring up an old thread, but how much will x amount of sodium hydroxide raise the ALK and PH by?

Thanks

40g of sodium hydroxide will raise the alkalinity of 1L of water by 1000meq/L.

The pH effect will depend in large part on what else is in the water but it will usually be rapid and massive.

I would strongly recommend against this idea. It's hard to control and has a very high probability of messing things up.

[Dan_P]

Originally Posted by Acromaniac

Sorry to bring up an old thread, but how much will x amount of sodium hydroxide raise the ALK and PH by?

Thanks

What's the reason for thinking NaOH might be useful for you?

[djbon]

It might help you with PH and ALK, the main concern for me will be salinity. I'm not a chemist, but when dosing sodium nitrate, i discovered that salinity is increased after a few dose. Maybe somebody can explain on this as well.

[bertoni]

The sodium in sodium nitrate and sodium hydroxide adds to SG. All two-parts raise the SG in this way, since they add either sodium carbonate or bicarbonate. They also add calcium chloride. The alkalinity and calcium are consumed, leaving sodium chloride (table salt).

[Dan_P]

Originally Posted by bertoni

The sodium in sodium nitrate and sodium hydroxide adds to SG. All two-parts raise the SG in this way, since they add either sodium carbonate or bicarbonate. They also add calcium chloride. The alkalinity and calcium are consumed, leaving sodium chloride (table salt).

That's true as stated but we need to do the math to understand the impact. Specific gravity of salt water is in parts per thousand and I am guessing sodium nitrate addition is in parts per million every so often. So, if someone puts some numbers in, i.e., how much how often in what size system, we can calculate whether the change is even detectable.

[djbon]

I used sodium nitrate (9mg/500ml RODI), after 2 complete course (1 liter) my SG raised by 0.002. I'm not sure whether chloride and sulfate will have impact on salinity as potassium chloride, calcium chloride, magnesium sulfate & magnesium chloride and calcium hydroxide are part of my dosing regime as well.

[Dan_P]

Originally Posted by djbon

I used sodium nitrate (9mg/500ml RODI), after 2 complete course (1 liter) my SG raised by 0.002. I'm not sure whether chloride and sulfate will have impact on salinity as potassium chloride, calcium chloride, magnesium sulfate & magnesium chloride and calcium hydroxide are part of my dosing regime as well.

Thanks for numbers. Overall, your addition should lower the specific gravity because you are essentially adding just freshwater with about 4 ppm sodium. The increase you noted is from something else like evaporation.

[djbon]

Thanks Dan. Will sulfate & chloride affect salinity as well?.

[disc1]

Originally Posted by djbon

Thanks Dan. Will sulfate & chloride affect salinity as well?.

ANY salt that you add will increase salinity.

When you add two part, even the carbonate and the calcium contribute to a rise in salinity until they are consumed by the corals. Their consumption equates to a decline in salinity that counterbalances some of the rise but not all as they leave behind the sodium and chloride.

1 ppt is 1000ppm so you can sort of gauge the rise from that. Forget the amount of freshwater that is involved as the level in your tank will stay the same. That is, if you add some sodium nitrate or something dissolved in RODI, then that represents that much less that your ATO will have to deliver that day.

[bertoni]

Some people report a 0.001 unit rise in SG per month due to 2-parts. I haven't done the math to compute the amount of 2-part required. If we just assume it's about 1 psu, that is about a 2.8% increase in salinity, or about a 5% addition in terms of dry weight, given that about half the supplement is consumed.