Making NaOH, 0.1M solution?

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Morten

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Hi.

Any chemists in here?

Want to measure TA in my wines using this method:

Can’t find NaOH solution, so thinking of making my own 0.1M from caustic soda, which is granulated NaOH.

Caustic soda has a molar mass of 39,997 g/mol (approximately equal to 40).

1M=40 gr/litre.
0.1M is 1/10 of 40.

So, if I take 4 grams of caustic soda in 1 litre of water, then I should have 1 litres of 0.1M. I THINK 🤔

Is it this simple?
 
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Yes, 4g/L of NaOH will give you a 0.1N solution. There are a few caveats however. Just as your 0.1N solution is not 100% shelf stable, neither is the solid form. It will absorb CO2 and water from the air, so over time what you weigh out won't be 100% NaOH. In fact it's deliquescent, so if you leave it long enough with enough humidity, you'll end up with liquid goo. (Also related, if you're going to buy NaOH granules/pellets, make sure they are 'lab grade', with a certified purity. I'm not sure I would rely on the stuff that is sold as drain cleaner.)

If a stock solution as suggested by @ibglowin isn't available, you could buy some dessicant to reduce water uptake in your solid sample. And store it in a vacuum jar if you want to get super fancy... :)

If you want to be as accurate as possible you could titrate your 0.1N NaOH with a known acid standard (potassium hydrogen phthalate, KHT is often used). I might do this one day just to see how far it drifts, but to be honest I just buy a new vial of 0.1N stock solution every year. From the morewinemaking.com link above, shelf life of an opened 0.1N solution is 3 months but I don't think the change in strength will have an actionable effect on my measurements. I use the leftover old solution to rinse my burette prior to filling with the new stuff.
 
Yes, 4g/L of NaOH will give you a 0.1N solution. There are a few caveats however. Just as your 0.1N solution is not 100% shelf stable, neither is the solid form. It will absorb CO2 and water from the air, so over time what you weigh out won't be 100% NaOH. In fact it's deliquescent, so if you leave it long enough with enough humidity, you'll end up with liquid goo. (Also related, if you're going to buy NaOH granules/pellets, make sure they are 'lab grade', with a certified purity. I'm not sure I would rely on the stuff that is sold as drain cleaner.)

If a stock solution as suggested by @ibglowin isn't available, you could buy some dessicant to reduce water uptake in your solid sample. And store it in a vacuum jar if you want to get super fancy... :)

If you want to be as accurate as possible you could titrate your 0.1N NaOH with a known acid standard (potassium hydrogen phthalate, KHT is often used). I might do this one day just to see how far it drifts, but to be honest I just buy a new vial of 0.1N stock solution every year. From the morewinemaking.com link above, shelf life of an opened 0.1N solution is 3 months but I don't think the change in strength will have an actionable effect on my measurements. I use the leftover old solution to rinse my burette prior to filling with the new stuff.
I am a amateur brewer, so I guess it will be both pure enough and accurate enough for my use. At least I choose to believe so. 🫣
 
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