# Vinoferm acid test: End point w/PH meter



## TNFISHRMAN (Feb 20, 2006)

What would the end point be with the ph meter on the Vinoferm test?? I know that the L.D. Carlson Titration is 8.2 just not sure about The Vinoferm and Indicating solution. Thanks, Lynn


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## TNFISHRMAN (Feb 20, 2006)

I found iton the indicating solution bottle. It's 7.0 for Ph with the Acidometer kit. 


Next Question: I have repeated the Acid tests over and over with the L.D. Carlson kit and the Acidometer. I am using fresh Sodium Hydroxide from George with the L.D. Carlson kit. Results with L.D. Carlson kit are .35%. With The Acidometer Kit purchased from George in November I am getting 5.5g/liter. What is up with these results I did the 4 different times with each kit and got the same result each time for the kit I was using. Would the Phenolphthalein solution being old throw off the results of the L.D. Carlson test? The END Point used on the L.D. Carlson kit was 8.2


Somebody help me out here, I am driving myself insane over this Acid testing. *Edited by: TNFISHRMAN *


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## masta (Feb 21, 2006)

Not really sure why the results are so different and wish I had an answer for you. The first thing that comes to mind is the lack of ability to stir the solution well when adding sodium hydroxide or indicating solution.


I have found it very difficult to get what I think is an accurate reading with the Vinoferm when doing it in the graduated cylinder that is supplied. I was lucky enough to acquire a mixing plate which I use to mix thesamples well while doing the testing.


Since there has been a few requests for a how to pictorial on this subject I will be ordering some fresh supplies and do some testing with both the standard Acid test kit and the Vinoferm and will post results with pictures.


Hopefully this will shed some light on this subject.


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## TNFISHRMAN (Feb 24, 2006)

thanks Masta!


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## masta (Feb 24, 2006)

I have placed my order for some fresh supplies and my plan is to complete the testing and post results next weekend.


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## Hal Maulden (Feb 28, 2006)

TNFISHRMAN,


When doing acid determination with a pH meter your looking for what is called an "inflection point". This is where your pH change is very dramatic. An example would be. You start with a wine sample that is 3.2, you start adding Sodium Hydroxide drop wise, allowing the pH to partially stablize with each several drops. At one point your pH is ~ 7.3, with the next drop it is 10.6 and the next drop it is 12.5. The value to record will be the amount just prior to the inflection.


Another thing to remember. With each vendor, the kits come with different strength NaOH. As example there is a huge difference with LD Carlson kit and Crosby and Baker kit. One is 0.1N NaOH and the other is like 0.5N NaOH. 


Next - When you calculate your acid it can be expressed as any acid. Sulfuric, tartaric, citric. It makes a huge difference on how this is calculated. Make sure that you are comparing apples to apples.





Hal


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## TNFISHRMAN (Feb 28, 2006)

Hal what is the proper way to know whether it is tartaric or citric? I would certainly assume that we would not have Sulfuric levels infine drinkable wine know would we?
From what I understand about what you said then When using the Vinoferm acidometer and a PH meter then I would watch for the next drop or drops to really cause the ph to take off towards the alkaline side then. In other words when I see that first big jump in ph thatwould be the end point?


Both NAOH's were purchased from George and should have been the LD Carlson brand and the same strength according to the bottle label. Thanks as always for you input, Lynn


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## Hal Maulden (Mar 1, 2006)

Lynn,


Without performing Paper Chromotography you cannot determine which acid is dominate. And even with that, PC does not give you %, because it is only a qualitative. In most, if not all, cases your wine will contain a mixture of Malic, Latic, Tartaric and possibly Citric. In many test kits that refer to the acids in PPT (parts per thousand) it is "expressed" as sulfuric. You are correct in that the wine does not contain sulfuric. What I mean by expressed is that when a titration is performed, there is a calculation that takes the amount of NaOH (base) used to nuetralize the acid and convert that, by calculation to be expressed as a particular acid. An example would be, if you did a titration and converted the acid to % latic and then calculated it and expressed it as % Sulfuric, the latic value would be a much higher % because it is a much weaker acid. In other words, it takes much less NaOH to nuetralize 1% latic than it would to nuetralize 1% sulfuric or tartaric.


Now, with this said, it really doesn't matter how you express it, just that you do it the same way all the time. In most cases the standard for most test kits is % tartaric. This is what i use and it works well for me. 


I hope this has helped.


Hal


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