Measuring the strength of a sodium hydroxide solution

[Reefs and Geeks]

So, this isn't directly a reefing question but more of a 3D printer question. lots of people use 3D printed stuff for reefing, so I think it might be relevant enough to ask here.

I have a 3D printer I use at work (and occasionally for personal reefing stuff) and we have a sodium hydroxide heated bath which is used to dissolve the support material from the 3D prints. We don't have a good indicator for how depleted the solution is and currently we just change it out whenever the support material stops dissolving, but I'd like to find a better way in which I can measure the concentration of the sodium hydroxide solution in order to better predict when the solution will need changed out.

The idea I had in my head was to take a sample of the solution and see what volume of some acid it would take in order to drop the pH to some level. What acid that might be, and what pH level and how to best measure the pH level is where I'm not sure how to start. Is there a color indicator for pH I can purchase somewhere instead of using a pH probe that would be suitable? Any recommended acids to use that would be safe?

TIA!

 

[Randy Holmes-Farley Verified Community Expert]

Do you know the solution strength when it is new?

An alk titration will do it.

 

[Reefs and Geeks]

Thanks Randy. I don't know the strength of the solution when new, but will get supplies to do an alk titration and will check it when new, and when depleted and use whatever that is as the usable range.