Sodium hydroxide

[Christoph]

In my opinion its the concentration aspect. A 50% NaOH solution has just so much more hydroxide present per droplet, compared to saturaded calcium hydroxide (which is of course also far from harmless, especially if dust gets in the eye).

Everyone using NaOH should just be aware of the risks and use proper precautions. NaOH should imo not be sold in "over the counter" reefcare products.

Best regards,
Christoph

 

[danimal1211]

Due to the size of my tank I took Randy’s recipe and further diluted it so that dosing could be more spread out. I use a a glass container for both mixing and dosing. I also keep my dosing reservoir low and learned the hard way not to submerge the other end of the tube (I now know how to make stalactites).
If the first time mixing doesn’t make an impression as to how caustic it is, I’m not sure what would. I use PPE whenever working with it.

 

[Randy Holmes-Farley]

In my opinion its the concentration aspect. A 50% NaOH solution has just so much more hydroxide present per droplet, compared to saturaded calcium hydroxide (which is of course also far from harmless, especially if dust gets in the eye).

Everyone using NaOH should just be aware of the risks and use proper precautions. NaOH should imo not be sold in "over the counter" reefcare products.

Best regards,
Christoph

I don’t disagree with that. My recipes are nowhere near 50% (about 7% or a bit under 2 M) and can be as dilute as folks want.

My recipe as written includes warnings:

Alk part

Add 283 grams of sodium hydroxide to 1 gallon of fresh water. It will get quite warm. Make sure it doesn't soften your container. This solution will contain about 1,900 meq/L of alkalinity (5,300 dKH).

BE CAREFUL WITH THIS SOLUTION: IT HAS A pH ABOVE 14. Do not get it in your eyes or on your skin. Keep all reef chemicals, especially this alk part, in a way that children cannot access them.

 

[Bakki]

Thanks all for your feedback.

Short summary as to why it is not commercially advertised is the health concern (and maybe the complication having to use multiple dosing methods to avoid overshooting the pH).

Perhaps a stupid idea but would it be possible to mix sodium hydroxide at a pH lower then 14.0 but higher than the max of kalkwasser (12.4?).
- Main limitation with kalk is that it is tied to water evaporation and its saturation point (pH of 12.4?)
- I would assumed that when mixed to the same pH kalkwasser and sodium hydroxide have the same effect on alk contribution?
- At what pH would you set a limit? I know kalk is already quite caustic but people clearly feel different between kalk and a sodium hydroxide mixture with a pH higher than 14 given the logarithmic nature of the scale.

 

[Miami Reef]

Sodium hydroxide and kalkwasser (calcium hydroxide) have the exact pH boost per unit of dKH raised. It doesn’t matter if you make it dilute or concentrated. What matters is how much alk you add.

I personally follow Randy’s recipe which matches the concentration of the standard calcium chloride recipe to easily dose one of each solution.

I’ve been having great success with it. I use BRS 1.1mL/min peristaltic pumps which are anti siphon and I use LDPE dosing lines which are chemically resistant to hydroxide.

 

[Randy Holmes-Farley]

Perhaps a stupid idea but would it be possible to mix sodium hydroxide at a pH lower then 14.0 but higher than the max of kalkwasser (12.4?).
-

Yes, I mentioned it can be diluted as much as you want.

For both kalkwasser and sodium hydroxide, the pH is a good measure of potency. Not perfect, but close enough.

 

[Randy Holmes-Farley]

FWiW, the reasons my hydroxide recipes are at the potency they are is to facilitate potency matching to carbonate recipes and allow use of online calculators.

 

[Randy Holmes-Farley]

For folks with low pH issues, having the pH get too high is an uncommon outcome.

 

[Miami Reef]

FWiW, the reasons my hydroxide recipes are at the potency they are is to facilitate potency matching to carbonate recipes and allow use of online calculators.

It’s much easier like that. Very simple to switch from one to the other without risking math errors.

 

[Sisterlimonpot]

And something else to consider is that sodium hydroxide doesn't raise calcium in equal parts like calcium hydroxide. So if you're using sodium hydroxide to raise pH you'll need to supplement calcium. Randy has a recipe for that.

 

[vahegan]

I have been dosing 2-parts with only sodium hydroxide as the alkalinity source for quite a few months now. I make a 120 g/l solution and I currently dose 50 ml of this solution per day. Actually per night, as I only dose between 9 pm and 9:30 am - I have developed this schedule to minimize pH variations. My pH is now getting to about 8.45-8.6 at the peak, and drops to about 8.3 before lights on. I like this approach much better than I was dosing sodium carbonate in the years before, even though that was supposed to keep my pH high.

 

[Bakki]

Is there a recommendation for the container and tubing used given the corrosive nature and the heat generated when mixing sodium hydroxide?

 

[elysics]

Is there a recommendation for the container and tubing used given the corrosive nature and the heat generated when mixing sodium hydroxide?

the main thing is to try not to get it hot while mixing or using glass to mix, and not using containers out of polycarbonate, most other common stuff should be fine

 

[Randy Holmes-Farley]

Is there a recommendation for the container and tubing used given the corrosive nature and the heat generated when mixing sodium hydroxide?

Once the solution is no longer hot, polyethylene, polypropylene, and pvc will all be fine at high pH. Too much heat can soften these.

 

[Miami Reef]

Plastic vinegar jugs are made of HDPE (high density polyethylene). RO tubing is also polyethylene.

I use clear polyethylene tubing for my dosing pumps.

I mix the sodium hydroxide in borosilicate beakers and transfer them into the old vinegar jug. It gets very hot while dissolving.