[xchcui]

Hi.

I saw on the web several cheap ph meters that are advertised as suitable for checking  PH of portable water,swimming pools,aquarium,food,beverage,in school laboratories etc.They usually come with ph buffer powder for calibration.On the attached photo you may see two types:the upper one is calibrated by a screwdriver (potentiometer) and the one below is calibrated automatic by the buttons.screwdriver(potentiometer) and the other is calibrated automatic by the buttons.
I know,according to wikipedia,that the ph meter:

...measures the hydrogen-ion activity in water-based solutions, indicating its acidity or alkalinity expressed as pH.The pH meter measures the difference in electrical potential between a pH electrode and a reference electrode, and so the pH...

Can this type(as in the photo)of PH meter be used to check
antifreeze/coolant 50/50(50% water/50% ethylene glycol)and give an accurate ph results?

Thanks.

[chenbeier]

I think it can, but why you need the pH in a coolant, there normaly no acids in. What is a  right pH in a coolant.  The glycol is a kind of alcohol.

[xchcui]

The PH value depends at the type of the coolant and it can be found in the coolant datasheet.If the PH decrease below a certain value(glycol breakdown),galvanic corrosion may happens.But this is not exactly the purpose of my question,i would like to focus on the PH meter,please.

[Borek]

Measuring pH of a solution that is only partially water is rather tricky - depending on the electrode it may give completely unreliable results.

[xchcui]

Measuring pH of a solution that is only partially water is rather tricky - depending on the electrode it may give completely unreliable results.

What about measuring ph of that partially water solution with PH strips?Are the pH strips a better option or will they experience the same
unreliable results as the pH meter?

[xchcui]

Hi.

I understand that pH meter may give a false results
in mixed aqueous/non-aqueous samples like in coolant/antifreeze(50/50).
Are the pH testing strips a better choice for that testing
or will they experience the same unreliable results as the pH meter?

Thanks.

[billnotgatez]

I merged your 2 topics since both have approximately the same question.

We only post a given question once on the forum.
This is a forum policy.
Click on the link near the top center of the forum page.
Forum Rules: Read This Before Posting.
http://www.chemicalforums.com/index.php?topic=65859.0

[xchcui]

I merged your 2 topics since both have approximately the same question.

We only post a given question once on the forum.
This is a forum policy.
Click on the link near the top center of the forum page.
Forum Rules: Read This Before Posting.
http://www.chemicalforums.com/index.php?topic=65859.0

Hi billnotgatez.

Do you refer to that rule?

4.6 Don't post more than once

I opened a new topic because no one replied to my new question,so i assumed that the new question should be asked in a new topic.
Okay,i guess i was wrong.
Thanks for your remark.

[xchcui]

Hi Borek.

From your experience,will the pH strips be a better option or will they experience the same unreliable results as the pH meter?

[Borek]

Hard to say, in general I wouldn't trust things designed to work in water when used in other solvents. They may work, they may not.

[xchcui]

Hard to say, in general I wouldn't trust things designed to work in water when used in other solvents. They may work, they may not.

Thanks,Borek.

[pcm81]

OP,
You need to ask yourself couple of questions before you can select best meter for you.

1. How accurate measurement do you need?
2. How large is your sample size?
3. What conditions are you making measurement in?

Here is why it matters:
1. If you are just looking for a large drift in pH ,you probably do not need a measurement accurate to 0.01pH. If you have a spec sheet which gives acceptable range of +/- 0.1pH then you probably want a meter that is 0.01ph accurate (this will cost $150 for reliable one).
2. If your sample size is just couple of drops, then you are kind of stuck with ph paper. If your sample size is like 50ml then you can actually use real meters.
3. If you are doing the measurement outside in bright sunlight or in dark and dim basement will determine how much PITA it will be to use color driven ph tests like ph paper.

After owning a $20 ph meter that supposed to read 0.1pH accuracy and then owning a $30 ph meter that supposed to read 0.01pH accuracy i ended up buying a $150 pH meter that rads 0.01pH accuracy and could not be happier. You might be able to get away with using cheap meter (potentiometer calibration) for a ballpark measurement if you calibrate it at Ph close to what you are measuring and you always measure small range of pH values, say 6-9pH. Also, if you are going to go the "cheap potentiometer based meter route" consider pH meter with 2 potentiometers, one for slope and one for offset. You really need to adjust both to get a decent reading over a deently wide range of pH values.

EDIT:
Also, consider the temperature of the coolant. Unless you have a coolant sample sitting comfortable on a table at room temperature for all your tests, you probably want a temperature compensated pH meter; otherwise you can fool yourself into getting wrong / changing values due to variance in temperature of the test sample.

[Orcio_87]

Can this type(as in the photo)of PH meter be used to check
antifreeze/coolant 50/50(50% water/50% ethylene glycol)and give an accurate ph results?

Yes, but due to different ionic product of solvent, standard pH scale will be disturbed (neutral point will be else than 7).