pH meter & Acid Additions

[Guttoc27]

Just got a Milwaukee MW102 meter. Calibrated it per instructions. Checked the pH of a 1 Gallon sample of water and got 6.85. For fun, added 0.1 grams (tiny tiny bit) of Acid Blend. Retested it and came out to 3.98. That seems drastic for the tiny amount of acid blend I added. Thoughts? The buffer solutions keep checking out ok.

Thanks!

 

[cmason1957]

One thought is that the acid blend wasn't fully incorporated (or mixed) into the water. The 6.85 doesn't seem really wrong. Pure distilled water might be 7.0, but any other water, who knows.

 

[Guttoc27]

I thought about that. But I let the water sit for quite a while and stirred really well. Same result. Is there a standard time to wait after the addition of the acid blend, before readings can be trusted? Thanks!

 

[Stressbaby]

When I'm adjusting my must, I add, stir thoroughly, check, add again, stir thoroughly, check, etc. I don't wait longer than it takes to be sure that it is fully dissolved and distributed, and then the pH is pretty close. When I leave it and check the next morning it might change by up to 0.1, but nothing really dramatic. I have the same meter.

YMMV

 

[Trick]

That is the chemistry. Clean water doesn't have too much buffer matter in and a little of acid makes big change. The story will be different in a must, where a lot of buffering material is there.
The other thing is, the pH scale is in logarithmic scale, from 7 to 4, a little bit acid will work. But from 4 to 3, you need to added 10 times more acid. and for 3 to 2 you need to add 100 times. etc.