Acidometer - Vinoferm

[Goslin]

Is any one familiar with their use? I ordered one from another place
before I found this site and it was missing the litmus papers. Is it
possible to use with out the papers? Useing it without papers I'm
getting a good reading of 7 on the cylinder but the ph is off the
scale, showing way to much acid. If any one has used this, generally
how much more solution have you had to add in the past after the color
change in the cylinder using the litmus paper to get a more acurate
reading. I'm basically trying to guess what my acid level is based on
how much extra solution others have had to add after the color change
in the cylinder.

I hope this is making sence. I also realize if it could be done this
way that the papers would be nessasary to begin with. Like I said I'm
just trying to get a rough guess until the papers get here.

 

[masta]

I have used one with a few tests and once you see the color change you should be all set as the few I did with the paper check showed it was correct. I found it tough to get a good mix in the cylinder so I used a 50ml beaker.


You say the pH is off the scale....what scale is this?

 

[Goslin]

Ph paper. They start out purple but in two tests for two different
batches they turn a bright yellow which is way off the scale to compare
the paper with. I'm begining to think the problem is with the ph
testing it self, every thing I've read about the ph litmus papers has
been bad news. I've been practically pulling my hair out trying to
figure out what's wrong when in reality the wine could be perfectly
fine. And according to your post it most likely is. Thanks.

Looks like I'll need a ph meter as well, I no longer trust the ph papers.

 

[Goslin]

Thanks, Thanks, Thanks, Thanks THANKS! This is very good news.

 

[Joseph1]

If you are going to get a pH meter, you can place the Acidometer on the shelf with the other little used equipment. First put your sample in a 50ml beaker and take your pH reading (the meter must be calibrated first). Then to determine acidity, slowly add sodium hydroxide (using burette, pipette or syringe), stirring as you add, until you have a pH reading of 8.2. The titratable acidity of your sample can thenbe determined with the following formula:<?amespace prefix = o ns = "urnchemas-microsoft-comfficeffice" />

TA = 75 * V * C/VS

Where:

V = volume of sodium hydroxide needed to obtain a pH of 8.2
C = concentration of sodium hydroxide used (0.1 normal or 0.2 normal)
S = volume of the sample of wine or must

For example: you have a 15ml sample of wine and add 12ml of 0.1 normal sodium hydroxide solution to reach a pH of 8.2.

TA = 75 * 12 * (0.1 / 15)
TA = 6.0

The acidity of the sample is 6 grams per liter (6 parts per thousand or 0.60%). Note that this formula will also work if you use Phenolphthalein indicator solution since the color change occurs at pH 8.2

Play with the formula to adjust the sample and the concentration of sodium hydroxide solution. For example; if you use a 15ml sample and the concentration of sodium hydroxide is 0.2 normal, each ml of sodium hydroxide added translates into one gram per liter (0.1 %) of titratable acid.

Make sure the sodium hydroxide solution is fresh. It has a limited shelf life and begins to deteriorate once the bottle is opened. Buy the smallest bottle possible. Buy in bulk only if you plan to do a lot of testing in a short period of time. The alternative is to add to your lab and standardize the sodium hydroxide solution before using it in your test.

 

[masta]

Excellent post Joseph....I believe this would be a far more accurate way to test for the TA of your red/dark must or wine instead of looking for color change which can be difficult at times.

 

[Goslin]

Very good Joseph, thats the best way to measure I've seen yet. I've got it saved for future reference