pH Testing

[cheshamjim]

I think the pH in my water is testing about 7.4 or maybe 7.6. I have a devil of a time deciding where I am on the pH scale. Seems like there are two issues for me: color match and (for lack of a better term) translucence. In my latest sample, the color is kind of pinkish, more closely matching the colors in the 7.5 to 8.2 range. But the translucence most closely matches the lower range (yellowish) values of 7.2.

Yes, I am judging the samples in full daylight, holding the sample about 6" away from the white panel in the lid of the test kit case.

Is this a problem for anybody else?

-Jim

[waterbear]

Here is an easy way to tell the pH when using phenol red indicator (which is what is found in every test kit I have ever seen!)
If the color is red (actually more pinkish) or purple your pH is too high! 7.8 or higher
If the color is yellow to yellow orange your pH is too low 7.0 or lower
If the color is orange to orange red your pH is perfect 7.2-7.6

You are looking for the color of the indicator..not how deep or light the color is!

A good way to learn the colors is to put some water in a small vial with a cap,add some phenol red so you can see the color well but not so much that it's very deep. add a TINY pinch of borax, cap and shake to make the color purple, then add vinigar drop by drop and cap and shake after each drop and watch the colors change from purple to red to orange to yellow. Phenol red will test pH from 8.2 down to 6.8....purple means 8.2 or HIGHER, yellow means 6.8 or LOWER. An orange color is about 7.4-7.5 which is pretyy much perfect!

[brent.roberts]

get your wife or GF to look at the colors.

The have a better eye for the differences.

[cheshamjim]

I haven't had a chance to try Waterbear's suggestion yet, but this is a good thought, Brent. Maybe I'll get both of them to look at it. :D

-Jim

(...aw, they're one in the same.) :)

Brent, I'd like to meet you over on CarlD's Dolphin thread 'cause I've got a question. See you there?

[cheshamjim]

Evan, I tried your suggestion of using borax and (white) vinegar to bring a water sample through a range of colors representing high to low pH. The colors showed beautifully beginning with something in excess of 8.2 and changing to the orange that represents the the more acid. I got to a point where the color matched the 7.5 sample perfectly. Then I added one drop of vinegar (with a medicine dropper) and the resulting color matched 7.2 perfectly.

I did not experience the ambiguity (or translucence) of color that I experience when I test my pool water. So I've got to say that the experiment for me was somewhat inconclusive.


I do appreciate your suggestion and the attempt to help.

-Jim

[waterbear]

The color is the only important thing. match the colors. I really don't underatand what you mean by translucense. Do you mean the intensity of the color?

[cheshamjim]

Evan, I tested my pH this a.m., keeping your suggestions in mind - the color is the thing!

Looks like my pH is at about 7.8, definitely purple, just not quite as intense a purple as the color at 7.8 on the comparator. However, the sample doesn't have that yellowish tinge that the 7.5 scale has.

Since I can't explain what I mean by "translucence" I'll give up on that term and just remember to pay attention only to the color no matter how translucent it is. :)

Thanks again for your help.

-Jim

edit: maybe intensity is the word.

[grangerhj]

Here is an easy way to tell the pH when using phenol red indicator (which is what is found in every test kit I have ever seen!)
If the color is red (actually more pinkish) or purple your pH is too high! 7.8 or higher
If the color is yellow to yellow orange your pH is too low 7.0 or lower
If the color is orange to orange red your pH is perfect 7.2-7.6

You are looking for the color of the indicator..not how deep or light the color is!

A good way to learn the colors is to put some water in a small vial with a cap,add some phenol red so you can see the color well but not so much that it's very deep. add a TINY pinch of borax, cap and shake to make the color purple, then add vinigar drop by drop and cap and shake after each drop and watch the colors change from purple to red to orange to yellow. Phenol red will test pH from 8.2 down to 6.8....purple means 8.2 or HIGHER, yellow means 6.8 or LOWER. An orange color is about 7.4-7.5 which is pretyy much perfect!


Waterbear- this should be a sticky so that all newbies can truly understand what they are looking at. THIS IS A GREAT DESCRIPTION- thank you

[waterbear]

Evan, I tested my pH this a.m., keeping your suggestions in mind - the color is the thing!

Looks like my pH is at about 7.8, definitely purple, just not quite as intense a purple as the color at 7.8 on the comparator. However, the sample doesn't have that yellowish tinge that the 7.5 scale has.

Since I can't explain what I mean by "translucence" I'll give up on that term and just remember to pay attention only to the color no matter how translucent it is. :)

Thanks again for your help.

-Jim
What test kit are you using. Sounds like the problem is your comparator. Some of the cheaper ones just don't match the colors of the indicator very well. the Aquachem test kit is a good example of this! That is one of the reasons why it is worth the money to get a good test kit like Ben's ( or one from Taylor or LaMotte).

edit: maybe intensity is the word.
Intensity of color is where the cheaper comparators usually fail. If you are seeing a purple color your pH is definately about 7.7 or higher. 7.5 will have a definite orange color with just a hint of red in it. 7.6 is a faily pure pinkish red color.

[cheshamjim]

I'm using the OTO/Phenol red testkit that came with Ben's testkit. Maybe I should try to find a better color comparator somewhere?

-Jim

[waterbear]

I'm using the OTO/Phenol red testkit that came with Ben's testkit. Maybe I should try to find a better color comparator somewhere?

-Jim
That's one of the best ones out there and I have found that the colors match up almost perfectly!. Hold the tube in front of a white background (the inside of the lid) in the sun a few inches in front of it.

[cheshamjim]

Yes, I am judging the samples in full daylight, holding the sample about 6" away from the white panel in the lid of the test kit case.I've been doing that. I probably have some color perception deficiencies.

Thanks,

-Jim