TA results odd, finally testing and confused

[Jared Retter]

Finally got my wines tested with vinmetrica 300.
Results: Cabernet TA 5.98 when using 5ml sample. PH of 4.02. When using 5ml sample plus 15ml distilled water ended up at 9.975 TA? PH of Distilled water was also around 4, not 7 like I read it should be?
Syrah: also TA of 5.98 (I find this odd) and ph of 4.04
Estate red blend from a friend: PH 3.50 and TA of 6.38.
Just finding myself frustrated to get exact same number on TA but maybe it is closely related to ph?
ill test some whites tomorrow and see what I come up with.

 

[Ajmassa]

I found this happening with the distilled water to me as well. It never reads 7. I just stopped diluting eventually. Using a little shot glass the 5mL sample and NaoH is just about enough to get the ph meter submerged for readings.

 

[ceeaton]

1) Do you have any residual CO2 in your samples? That can have an effect on your readings.

2) How old is your NaOH solution that you are using to test TA? I've had issues in the past where my solution was weak (hence the TA "tested" higher). I use this https://www.piwine.com/potassium-acid-phthalate-n10-solution.html to test my normal solution.

 

[stickman]

@ceeaton has some good points to consider. Also, distilled water has no buffering capacity, so the slightest acid or base added will drive the pH in the corresponding direction. A 15ml sample of my distilled water reads 6.3 pH, adding 1 drop of .01N NaOH (almost nothing) caused it to move up to 7.4 pH, so unless your distilled water is badly contaminated, there should be no significant effect on TA using 15 ml for dilution.

 

[ibglowin]

pH electrodes will NOT give accurate pH values in distilled or deionized water. This is because distilled and deionized water do not have enough ions present for the electrode to function properly. The readings will drift and be essentially meaningless. pH buffers are the best solutions in which to test your pH electrodes. Tap water usually has enough ions present to allow a pH electrode to function properly. Because of this, tap water can be a good short term (~24 hours) solution for storage.

Also, keep in mind that water (distilled, deionized, or tap) is NOT "pure" (i.e., pH equal to 7). The moment it comes in contact with air, CO2 gas begins dissolving into it, forming carbonic acid. The actual pH, therefore, will often be slightly less than 7.