YT2095
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a Simple ph meter
I`ve put this in here under the Manufacture of, and the Asparatus banner.
all you`ll need is some Alu and Iron metal in rod or bar stock form, and then a cheap little digital volt meter.
the Iron can be a Nail, but idealy you want to get an OLD Nail, maybe out of a tin in your grandfathers shed or something, as for the Alu, you can use
a strip of sheet alu or even certain tent pegs, it doesn`t matter if it`s magnalium either, both will work.
needless to say, one metal goes onto one of the meters leads and the other metal on the remaining one (it doesn`t matter what metal goes on pos or
neg).
you`ll find that when you immerse these metals in plain water you`ll get little reading (set to the 2volt range).
now the reason to use a Digital meter is that it will show a (-) sign on reverse polarity.
with your 2 metal rods push them through a cork and glue them in place (or any other way you can that will hold them in place at a fixed distance).
it`s important about the fixed distance for calibration later, although the distance can be several metres appart IF you want.
(I`ve done this in soil a good 1.5m appart and it still works).
when both electrode probes are fixed in place attatch the meters wires, one to each.
put the metre on the 2 volt setting (or 1V if you don`t have a 2, adjust accordingly).
and you`ll find that you`ll get a Voltage reading in Alkaline and in Acid, one will be in (-) the other in the (+)
use known ph stock solns to calibrate the readings and note them on paper, with a wide range of solns and ploting these on a graph, you will work out
a curve.
from there staple that curve chart to your Lab wall and just use it 
I needn`t point out that it`s essential to clean the metals after each Dip/test to avoid contamination need I?
also clean well and dry when you`ve finished using it.
it`s only a simple and somewhat crude method, but you`ll find it has a multitude of applications idealy suited for such a thing.
Enjoy
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Oxydro
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| Quote: |
I needn`t point out that it`s essential to clean the metals after each Dip/test to avoid contamination need I? |
No, you needn't, because anyone who cares about contamination will realize that there will be metal ions from electrodes flowing into the solution.
Right? Or am I missing something?
"Our interest's on the dangerous side of things" -- Browning
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jimmyboy
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yes - it would work but then you have metal contaminating your solution -- i guess you could always take a small amount and do this if you had to..
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woelen
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Any chemical sensor will introduce at least some contamination, there must be something to interact with the solution, otherwise there is no
measurement. If I were to use a pH-meter (any meter, beit a professional one, or the one, proposed here) and i would not like any contamination, then
I would take a small sample of my solution and use that for the measurement.
Isn't it exactly the same with pH-indicators. These also introduce contamination and normally, if you don't want you main solution to be contaminated,
you take a few drops and put that on pH-indicator paper, or you add a few drops of your indicator solution to a ml or so of the sample taken from your
solution.
I still can imagine that you need to clean the electrodes after each measurement. Not for preventing cross-contamination, but for keeping good
measurements. Taking some liquid from one sample into a second sample will affect the measured result for the second sample.
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unionised
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If you could use 2 bits of scrap metal why would anyone ever have introduced real pH meters? Does it actually work?
If, for example, you measure the cell voltage with vinegar then add salt to the vinegar does the voltage change? Adding a neutral salt shouldnt make
any difference to the pH, but I suspect it will influence the voltage.
[Edited on 20-7-2006 by unionised]
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YT2095
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it does indeed work, I actualy found it out purely by accident when I measured the continuity across 2 ground (earthing rods) that I use for my VLF
receiver projects, there was a clear DC voltage.
get a simple nail and the ring pull off a beer can, push them inro the ground (idealy moist) and you`ll measure a clear voltage (that`s what did next
after I checked the ground rods).
I took this concept back to the lab and tested it, the voltage will not only Change with soln strength, but will infact reverse polarity between and
Acid and a Base.
test this yourself, some dil HCl in a beaker and perhaps some NaOH soln in another, then use a nail and strip of alu foil or tent peg or anything alu
really. you will see the principal in practice, you can refine it in whatever way you want afterwards.
as I said, it`s Crude, but it does work quite nicely for a few applications
Edit: In addition, it might be possible to use something else instead of Iron metal as the other electrode, I`m guessing that key lays in the Al metal
being amphoteric and changing its electode potential with Acid/Base thing. perhaps Carbon may be used instead, it`s certainly quite neutral as a
reactant in many wet synths.
as for the addition os neutral salts, Good idea! I`ll try that 
[Edited on 20-7-2006 by YT2095]
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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