My Aeration-Oxidation Free SO2 Setup

[ibglowin]

Just finished setting up one of these and thought I would post some notes.



Pretty simple, easy setup. Parts can be obtained from a variety of sources including eBay, Amazon etc. Its the chemicals (and their cost) that can be a big drawback over the simple (Accuvin) test kits. Since I am a chemist by trade, its not so much a problem for me. Biggest expense is finding 25% solution of Phosphoric acid. Since it is a hazardous solution, UPS charges a premium for delivery. These chemicals also have a limited shelf life and should be refrigerated between uses. Order/makeup only what you think you will use up in a 6 mo time frame.




Accuvin test kits are fine for probably 90% of the home hobbyist.

This test takes 5 minutes to setup, 15 minutes to run each sample and then 10 minutes to clean up and put away.

My particular problem is that I have limited color definition and all my Accuvin test seemed like they turned out all the same color (to my eyes)

Very hard to discern the correct color in any kind of light. This test provides an easy (huge) color change that even my eyes can see quickly. The endpoint can be detected within a drop or two. Not much room for error in endpoint detection. Again good for my eyes!

The burette and mag stirrer are not a necessity, again chemist by trade. Most people can get by with a 10ml plastic syringe and just swirling each addition. The mag stirrer does get it into solution in a split second so you can see the approaching endpoint much faster. Much less chance of overshooting the endpoint.

20ml sample of wine is required




When the Phosphoric acid is added to the wine any SO2 is reacted with and liberated from solution. The SO2 gas is flushed from the sample vessel over and trapped into the reaction vessel. The reaction vessel has 10ml 3% Hydrogen Peroxide (same as the grocery store kind), 6 drops of SO2 indicator solution (found online) and 40ml distilled H2O.




The (now acidic) Sample is titrated back using 0.01N NaOH solution. (found online). Drops are added and stirred until the solution turns from the vivid pink to a grey color. End point is then right at the change from grey to green.





The Free SO2 is calculated by taking the amount of NaOH required and multiplying times 16.

In this instance I used (3.0ml NaOH) X 16 = 48ppm Free SO2

All in all I find this a very accurate (and fun) test to run. In the 3 test I have run to date I am finding that my wine is pretty close to perfect just before bottling using the normal addition of 1/4 tsp K-Meta every 3 months. I have been able to cut back from a full dose just before bottling to a much more controlled addition based on the pH level of the wine as well as an accurate assessment of the free SO2 in the wine.

 

[Randoneur]

Nice well presented instruction for those of us looking to get more accurate measurements. Does't look much harder than most other tests.

 

[Runningwolf]

Very cool Mike and I like how you never stage the backgrounds in your pictures (monitor LOL). Thanks for sharing.

 

[ibglowin]

Had to get rid of the swimsuit model just for that shot!

 

[grapeman]

What kind of pump is that Mike? I assume it pumps air but is it vacuum or compressor like an aquarium pump?

 

[ibglowin]

$10 Aquarium pump. It does have a small valve to regulate the air flow.

 

[AlFulchino]

thanks for sharing Mike..i wish you were readily nearby for things like this!

 

[Randoneur]

Mike,
Did you usepipettes instead of fine point burettes to induce the air?
I assume the opening size on the trapped SO2 flask is important for good acidification.

 

[ibglowin]

One of my sparging tubes broke while trying to get it inserted.

I found that a 2ml disposable pipette was pretty much a dead match so I scored it at the right length and popped it in half. Works perfect. I used a little silicon grease to get them inserted through the #5 Stoppers.

 

[robie]

This sure makes it easier for testing red wines.

 

[SBWs]

I have tried this set up and found it works very well. I did find that the NaOH solution is very important it must be .01N and also the amount of the wine sample is another thing that has a direct effect on the out come. Multiplying by 16 only works if the wine sample is 20ml. Maybe George can start selling some of this stuff.

 

[Randoneur]

Full formula which accounts for molearity and sample size (from WineMaker Magazine):
SO2 (ppm) = (mL NaOH * N NaOh * 32 *1000)/ mL sample size
 
example:
SO2 (48 ppm)= (3 mL NaOH * 0.01 N NaOH * 32 * 1000) / 20 mL sample size
 
Stick to using 0.01 NaOH and 20 mL sample and its just the 3mL NaOH added x 16.

 

[ibglowin]

Good point! I left that little detail out in my calculation.

0.01N is dilute enough in that you can easily measure out enough and not go past the end point in a single drop. It will take you up nice and easy as long as you are dropping one or two drops at a time.

 

[SBWs]

I was reading on another board that citric acid could be used in place of Phosphoric acid, and also if you use a 32ml sample you multiply by 10 (easier to do math in head) So I made up a solution with 1 gram of K-meta to 1 gallon of water which according to Jack Keller 's site should be 150 ppm SO2. I then added 16 ml and 16 ml of distilled water to the flask for a 75 ppm sample. Then added 6 grams of citric acid and ran the test and came out with 60 ppm. Wasn't off by much. Didn't have anymore phosphoric acid to run another test to see what that came out to. The K-meta is 6 months old and my gram scale isn't the best. I'm thinking the citric acid might work and be a lot easier to get hold of. Wondering if anyone else has ever tried other acids.

 

[ibglowin]

I read that tile and grout cleaners (at least some so make sure and read the label) available from all hardware stores contain 25% phosphoric acid. I have not had a chance to check it out yet.

 

[Randoneur]

I'm getting ready to buy more Phos acid. Just wondering if you've found somethingto use in order to avoid the HAZ shipping cost??


Did the tile and grout cleaner work? If not I'm going to have to findone the lab supply houses here that will sell to me.


I looked a Hydroponic "acid down", but it looks like it has small amounts of other acids added to the phos.

 

[ibglowin]

I haven't really looked. I have access to Con Phosphoric that I just dilute down.

 

[wine_wizard]

So I have tried the "blue box store" tile and grout cleaner... as the phosphoric acid.

a) using test tubes ( not the flasks ) i had an issue with "foaming" (bubbles) filling the wine/acid tube and going up into the hose going to the "indicator" tube.

b) suspect that there are additives to the cleaner that in fact may encourage that ( and that chem lab phosphoric acid would not have those )

( btw, another trip to the aquarium dept, got me a "manifold" for aeration stones that allowed me to regulate the air flow volume nicely from my pump )

c) the directions i used said to go for 15 min and then titrate back to original color which i did, but out of curiosity i let the aeration continue, and after another 5 minutes needed another drop or 2 to maintain color.
This continued for an hour ( at 5 - 10 min points ) at which time I ended.

suspect (1) the acid is weaker then the 28% and (2) that the "bubbles" delay the release of the so2 into the indicator container... between the start (15) and end 60 min i had a 3 to 1 ratio of "measured" so2 ...

 

[doughowe]

So I have tried the "blue box store" tile and grout cleaner... as the phosphoric acid.

a) using test tubes ( not the flasks ) i had an issue with "foaming" (bubbles) filling the wine/acid tube and going up into the hose going to the "indicator" tube.

b) suspect that there are additives to the cleaner that in fact may encourage that ( and that chem lab phosphoric acid would not have those )

( btw, another trip to the aquarium dept, got me a "manifold" for aeration stones that allowed me to regulate the air flow volume nicely from my pump )

c) the directions i used said to go for 15 min and then titrate back to original color which i did, but out of curiosity i let the aeration continue, and after another 5 minutes needed another drop or 2 to maintain color.
This continued for an hour ( at 5 - 10 min points ) at which time I ended.

suspect (1) the acid is weaker then the 28% and (2) that the "bubbles" delay the release of the so2 into the indicator container... between the start (15) and end 60 min i had a 3 to 1 ratio of "measured" so2 ...

Hi All. I just finished testing using sulfamic acid in place of phosphoric in my AO tests. I got sulfamic acid as a powder in the tile section at Home Depot. So far a 1% w/v solution used in place of the 25% phosphoric acid seemed to work fine, and no foaming or other issues from additives in other tile cleaner products. That comes down to something like a quarter teaspoon per 10ml H2O to make the acid solution. For 6 or 7 bucks I got enough phosphoric acid for hundreds of tests, and it should be pretty stable in the dry form so it won't go bad. Might even be able to use less...didn't try that yet. The only caveats is I haven't tested it with wine yet...only with sulfite standards made up in water. Wine has buffers so there is a small chance it won't work the same with wine..might take more..not sure..but it looks promising. Thought I would share in case someone else wants to give it a whirl. Very economical compared to phosphoric...
Doug

 

[doughowe]

Hi All. I just finished testing using sulfamic acid in place of phosphoric in my AO tests. I got sulfamic acid as a powder in the tile section at Home Depot. So far a 1% w/v solution used in place of the 25% phosphoric acid seemed to work fine, and no foaming or other issues from additives in other tile cleaner products. That comes down to something like a quarter teaspoon per 10ml H2O to make the acid solution. For 6 or 7 bucks I got enough sulfamic acid for hundreds of tests, and it should be pretty stable in the dry form so it won't go bad. Might even be able to use less...didn't try that yet. The only caveat is I haven't tested it with wine yet...only with sulfite standards made up in water. Wine has buffers so there is a small chance it won't work the same with wine..might take more..not sure..but it looks promising. Thought I would share in case someone else wants to give it a whirl. Very economical compared to phosphoric...
Doug

Hi,
Thought I would report final results I've had with sulfamic acid in place of 25% phosphoric. I noticed that the rate of color change in the peroxide solution was a bit slower than what I was used to when using phosphoric acid. So, I've upped it to 2% w/v sulfamic acid and it works great! No foaming problems and you can adjust the acid concentration higher even if you think it is necessary for your wine. The wines I tested tonight all worked great with the 2% sulfamic acid and 15 minutes of aeration. I recommend it. Good luck and keep testing...it's the right thing to do!
Doug