heads up ............

I've given up on using NaOH. I'm finding consistently reliable readings with the acidometer test kit. It's easier, cleaner, less measuring, etc.

Lee

I think there was a bit of a flap over that same issue two years or so ago. Instead of being 0.2N NaOH solution, what was in the acid test kits was nearly 0.4N, so all the acid measurements indicated there was about half the actual level of acidity. The LD Carlson folks were properly apologetic, claimed their supplier had messed up. But that wasn't much satisfaction for those who had added lots of unnecessary acid to their wine, based on bad measurements.

I decided at that point to make my own NaOH reagent, so I spent about $10 and got a lifetime supply of NaOH crystals. 0.2N works out to 8 grams per liter, and a liter will last me a whole season or more. So my couple of pounds of reagent should last me for about another century or so of winemaking, assuming I keep it dry. :-)

Doug

So

That is the key, it's hygroscopic. I have a friend who is a chemist and he said that was it's biggest drawback, it sucks in moisture like a sponge...

Joe

Yep, and if you want to dry it out, you have to bake it for about 24 hours at 125C (about 250F) in a nitrogen purged oven. Not many of us have one of those at home.

Gene

It will not only absorb moisture, it will also suck up carbon dioxide from the air to form sodium carbonate. That will also throw all of your calculations off.

You could, however, standardize your solution by testing the amount of acid in a known mass of tartaric acid, and fix your calculations that way.