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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Dynamin on January 30, 2019, 02:43:16 PM

Title: Calibrating PH meter
Post by: Dynamin on January 30, 2019, 02:43:16 PM

I'm having a b$*%( of a time calibrating my PH meter with those 3 solutions.
I was wondering, would it not be easier to just calibrate my meter by sticking it in some white vinegar, since that is always a 2.4 PH??

Thank in advance

Title: Re: Calibrating PH meter
Post by: chenbeier on January 30, 2019, 03:22:27 PM

This would be not very accurate. Vinigear is naturla product and amounz of acetic acid differs. Zou need a curve not only one point. You have to to know in which range you have to measure.

Acidic solution: calibrate with pH 7 and pH 4  or lower.
alcaline solution: take pH7 and pH 10 or higher.

Title: Re: Calibrating PH meter
Post by: Borek on January 30, 2019, 07:10:44 PM

Quote from: Dynamin on January 30, 2019, 02:43:16 PM

white vinegar, since that is always a 2.4 PH??

It is not.

Title: Re: Calibrating PH meter
Post by: Dynamin on February 02, 2019, 03:32:51 PM

Okay, so I finally have the darn thing calibrated properly.  Now I'[ve got another problem.
I've made a topical solution containing vitamins, minerals and amino acids.  Whenever I buffer it to PH7, and I then leave it at RT for a few days, the PH is somehow magically gone up to 7.5 or 8.0.

How can that be??

It cant be the PH meter because whenever I test it on the calibration fluid its spot on

Title: Re: Calibrating PH meter
Post by: billnotgatez on February 03, 2019, 02:21:41 PM

Carbon dioxide?

Title: Re: Calibrating PH meter
Post by: Dynamin on February 03, 2019, 02:32:07 PM

Quote from: billnotgatez on February 03, 2019, 02:21:41 PM

Carbon dioxide?

CO2 would make the PH go down, not up. Would it not??

I think it might be going up because I have quite a bit of undissolved solids in the solution.
So I guess my next step should be to microfilter them all out

Title: Re: Calibrating PH meter
Post by: billnotgatez on February 03, 2019, 02:44:49 PM

I apologize
I misread your post.
You are correct - Aqueous carbon dioxide reacts with water forming carbonic acid.