Got one for a birthday present back in the mid ninties and never went back to the chemicals.

But whenever I tried to find out exactly what they do all I get is, what to me is word salad, that the glass probe measures the "light of protons" in the solution and judges from there.

Does anybody have a better answer?

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pH is a measure of the concentration of protons in an aqueous solution. Acids increase the proton concentration, bases decrease it. The scale goes from 0 to 14, zero is the most acidic, seven is neutral, 14 is the most basic. It is a log scale, so a pH of 3 has ten times the number of protons as a pH of 4.

A pH meter is one of several technologies to measure it.

Is that the kind of answer you were looking for?

(footnote - and technicially, the correct way to type it is small p, capital H)

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At night the stars put on a show for free (Carole King)

One Earth, One Sky - IYA 2009

Swift, I've been eating, drinking and breathing pH since the early 80's when I started keeping aquaria. Got me fair and square on the spelling though. I'm tired this morning.

I just wondered how the meter worked. What "light" do protons give off? How do protons penetrate the glass probe. Etc, etc.

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You know I never realy thought about this (admittedly its been a while [read a couple of years] since I last used a pH probe) its just one of those things that never really crossed my mind: put probe into solution, press button, write down number, end of story but its an interesting question! so I decided to look it up, wikipedia says that they're basically voltmeters but as with most things on wikipedia actual accuracy is subject to change I am no electronics engineer so the actual description of how they work just causes me to go cross-eyed.

Sorry, I meant no offense. Since I've been drinking OJ and coke since the early 60s, I guess I've been drinking pH since then.

"Light of protons" sounds like absolute nonsense. The person may have misspoken. pH is a potentiometric (as in electrical potential) measurement, it has nothing to do with light measurements.

This website is a good start. This website has particulars about glass pH electrodes. As far as the glass, it is a speciality type, actually like a thin membrane of glass, that allows protons to go through it.

Let me know if you need more details, I'll dig out my old Instrumental Methods of Analysis textbook.

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At night the stars put on a show for free (Carole King)

One Earth, One Sky - IYA 2009

Ain't that the truth. Got to the point where if I had to inspect one more fish nose...



I swear, rich people can never settle for a simple tank either. BIG. Back Lights. I'm surprised they don't train the fish to play orchestrated music...
So you build them the tank into a wall or something and then ask about what kinds of fish...

No, they pick all salt water fish. Most exotic and impressive or prettiest.
After rebuilding the tank...
You set their system up- leave them three pamphlets and four books on home aquarium care and a box of goodies, food, chemicals, medical testing for fishy diseases and medicine... and I usually installed a thermometer, and a little visual aid of ailments on the side...



You get a call a week later and propositioned to get paid to take care of their fish for them.

Not just protons - specific cations (H+, Na+, Ag+).

http://en.wikipedia.org/wiki/Glass_electrode

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"Those who cannot remember the past are condemned to repeat it" - George Santayana

Big Don. When you go to their links, you see a Nernst Equation. In it is a piece of equation that describes the voltage measured from a reference standard...E⁰....and another piece of equation that describes how that voltage fluctuates due to concentrations in the liquid (water for you)...the RT/nF times log[Q]. Different concentrations of acid cause different voltages to be sensed by the electrodes....and the voltages are calibrated on the readout scale....or digital readout, to indicate the concentration causing it. As you know, like earthquakes' Richter readings, it's a log scale with each whole unit a factor of 10 higher/lower than its predecessor.
You'll be happy to know that my curiosity for things that are different led me to pick up a Portuguese Man-O-War as an eight year old on Chatham's Ridgevale Beach as a kid. Though dead, the nematocysts still worked fine teaching me a healthy respect for marine organisms everywhere. pete

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A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

Thank you again, Trin.

Man, I know about getting stung! I'm now sensitized to the venom and protiens of Cnidarians to the point of anaphalaxis.

At first it was getting tangled up in the carpet anemones, which is extremely unpleasant. Made me reconsider how pain and heat senses differ. As the bastards are very sticky you have a lot of time to wonder just how the sensation of intense heat AND electric contact are being produced by the venom. Seeing as how all nerve sensation is just pressure, temperature and pain.

Then various corals took a dislike to me.

First it was just the ones who had gone to war and were producing sweeper tenticles. But soon I was stricken hard by an open brain coral. Weird, that one. When feeling threatened it exudes a short chain acidic venom that breezes right through unbroken skin and latex gloves. With the strong sensory illusion of a powerful heat flash. Saves having to have a actual stinger. Happened to me twice. (First without, then with the latex gloves.)

And then it got one of the cynical new boss' as I was watching. He's a nurse and didn't believe I as being stung through the gloves. If he hadn't been truely a sissy, I would of kicked his butt for how he talked to me then. Some of the regular customers were doctors from Genentech who told us how it was being done, later. (They bought the particular coral too)

One of my co-workers became sensitized to fish venoms. I always had a repoir with the lion fish, so they never stung me. He was nailed three times by lions so when he got tagged by a tiny little bumblebee goby his hand rapidly swelled to the point you couldn't distinguish his fingers. I recall the Boss let him have the next day off.

Whenever there is a big stranding of By the wind sailors (Tiny blue portugese manowars the size of walnuts with a hilarious reproductive stradegy.) I can't go to the beach for about a week and a half or more. If the wind is strong just the parts volitizing in the surf will start a reaction in me.

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Gimme a minute to read through Jay's latest observations...

Big Don. You're welcome. Try neoprene rubber gloves...the heavier hardware store variety. Many proteins can make their way through latex.....neoprene is much more impermeable. I'm thinking a little benzocaine in the tank might make them a lot calmer when you have to handle them too...like smoking bees to collect honey? Good science fair project. pete

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A third rate theory forbids
A second rate theory explains after the fact
A first rate theory predicts...A. Lomonosov

As others have said, it does not measure the light of protons. It has a semipermeable glass membrane which detects the hydrogen ion concentration by electrical means.

I have found pH probes to be quite delicate. They have to be kept wet and looked after carefully. If you find one in the back of a lab cupboard it almost certainly will NOT be working properly.

Even if you find one that isn't broken, you need to calibrate the thing often with standard buffer solutions.

Kzb, (didn't you used to have an avatar?)

Nowadays I don't keep fish (with an eye towards breeding) who require that close a watch as to pH. This was back when I was breeding cardinal tetras and other such Amazonian beauties. Tetras start doing the happy dance at a low carbonate hardness and pH's lower than 6. In my tanks it was about 5.6 to 5.8. In the wild they will spawn in waters as low as 4.3 (protects the eggs from fungus and bacteria)

Which reminds me I have to change water today. It being too rainy and cold to garden.

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Oakton's Testr 1 model (~US$70, ~6"X1.5") has proven to be a durable and reliable tool these past 2 years. Put away wet, calibrated twice a year, one battery replacement cycle...and it floats!

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I'll bet extremely rich people can afford the automated tank minders (just keep the hoppers full. It'll do the rest).

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I am Mugs, of the Alien clan of Usa, Nordamerica, a Terran, of Sol. A human.

Whoever says "perception is reality" is daft. It's merely an abstraction, and often not a very good one.

Extremely rich people hire the tank minders.

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Keeper of the Jabberwock

Mugs, believe it or not those tend to have an issue with humidity. And a steady diet of dry food sucks. Especially for marine creatures.

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Gimme a minute to read through Jay's latest observations...