SO2 Testing

I've considered using the Accuvin SO2 testers, but haven't because of cost and, more importantly, shelf life. Last July I wrote to Accuvin, specifically concerning shelf life, and they wrote the following:

"The current shelf life of our tests in 11 months for pH, 7 months for Malic, Lactic, TA and Residual Sugar, and for our newest kit, Free SO2, 4 months. We are working to extend the shelf lives with ongoing studies."

Their ease of use is certainly appealing - but until they have a better shelf life I think I'll wait.

Prior to knowing about the Accuvin tests, I did purchase a vacuum/aspiration set up - it is NOT cheap, and several solutions needed have a shelf life of 1 year, but it seems to be very accurate. Besides cost of the glassware and chemicals, the downside is the time it takes to set up and run the analysis - if you have a number to do it will take a while (and if I don't have a number to do, I don't want to take the time to set it up).

Ed

I've been running straight Ripper on my wines - even reds. It's quick and easy to do once you get the hang of it. The most expensive part is the

0.02N iodine standard, but that lasts a long time if properly stored. Use a 10 ml graduated pipette instead of a burette; they're a _lot_ cheaper!

I find that diluting the sample 50:50 with distilled water helps make it easier to see the end point in reds. It's also important to have well prepared starch indicator or you'll have trouble seeing the endpoint - even in whites.

Tom S

Tom - any chance you have this method and how you do it documented somewhere with your practical tips included?

thx, dan

Thanks Tom,

The soluble starch solution - is that something commercially available or something you mix?

The 25% sulfuric acid, do you keep that stored or dilute it when you need it?

Both. You buy the powder and mix it up as needed. It needs to be boiled before use to work the best. It'll grow mold easily, so boil it before storing too.

I have a 3 liter jug of 98% which I add 1:3 to water to make up a pint at a time. You want to be careful when mixing that stuff because it gets quite hot. Always add the acid to water with plenty of stirring.

Tom S

Thanks Tom, Do you have a source or a link for the starch powder?

dan

Dan, Go the grocery store and buy a box of corn starch. Mix about 1/2 a teaspoon of starch in a cup of cold water. Bring the cup of starch solution to a boil. Use when cool. Lum Del Mar, California, USA