Hydroponics. More Government nonsense.

[Salmon Egg]

Hydroponics stores tend to be boutiques with boutique prices. As I got into this hydroponics, I wanted to buy a pH meter. It is getting more and more difficult to get lab equipment and chemicals. As I got into this hydroponics, I wanted to buy a pH meter. I selected a Corning ChekMite because I thought I could rely on the Corning cachet. I found that VWR claimed that it was a restricted device. Presumably it was that because of the war on drugs. I finally got it from a scientific supply house.

This same house, however, will not sell me chemicals, primarily because of liability. Many such places will sell only to businesses and not to individuals. One of the last places around the LA area where individuals could get supplies, TriEss sciences went out of business when the owner died. When I was there, there was a notice that iodine crystals could not be bought with out some kind of a permit. Again, I think because of the misguided war on drugs.

I have been getting hydroponic nutrients at reasonable rather than the boutique rate3s that pot growers are willing to pay. I get formulations of all the nutrients in granular form. A few years ago, after Oklahoma City, I was at a fertilizer place where they still were selling bags of ammonium nitrate and potassium nitrate. I don't know how available these substances are are now. I am content to get the mixtures.

Well, I still do not have a good pH test method. The glass electrodes in pH meters tend to last only about a year and are expensive to repair. Using indicator solutions is awkward. I think that I am going to end up using some of the test strips.

Bill

-- Fermez le Bush--about two years to go.

[Mc.Germ]

You can also try to get color indicating titration kits. They are simple to use. They have a graduated flask to hold the sample and you count the drops to color change to get a pH or other wet chemical concentration like Chlorides or Nitrates. I have used these in manufacturing plant situations where operators need pH or cleaning chemical concentrations to do their job. No real lab skills or expensive to repair equipment needed.

If still want a digital pH meter you can get calibration solutions and do the servicing yourself. You should also be keeping a glass probe in deionized water when not in use. There are also polymer membrane probes you may want to look into instead of glass. If you know that you are always basic or acidic you could also opt for a generally more rugged conductivity probe and convert the number you get to pH.

Jim

[Salmon Egg]

Thank you for the information. I do have an indicator solution that will work although the pH meter is more convenient.

I have been storing the electrode in a pH7 buffered calibration solution. Would it help if I store it in a concentrated KCl solution? That seems to be the way the electrodes get shipped. Where can I get information on how electrodes fail?

Bill

[m.k.borkowski]

't store electrodes in DI or RO water - unless you want to damage them irreversibly. You may store electrode in DI/RO water for a short period of time - few hours at most - when doing a series of measurements. When stored for days or weeks keep it either in the solution provided by the electrode producer, or in the pH 7.00 calibration buffer - or in the KCl solution.

Borek

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[m.k.borkowski]

See my previous post. In general both pH 7.00 buffer and KCl solution should do the trick. However, you should check users manual - sometimes one solution is preferred over the other. n most cases it means producer tested the elctrodes in one of the solutions and is sure electrode will work correctly if stored this way. This doesn't necesarilly mean that the other solution won't work.

You mean how to find out if the electrode fails? If you can't calibrate pH meter, if the indications are fluctuating you know something is wrong. As long as you have no problems with calibration electrode is almost for sure OK. You may move electrode several times between buffers to see if it keeps displaying correct value, just don't forget to flush the glass each time with DI/RO water before dipping (to prevent buffer contamination, dilution shouldn't change pH, contamination can).

Borek

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[Mc.Germ]

Sorry. Brain fart. Glass electrodes should be stored in the pH4 KCL buffer solution. To recondition a probe, soak it overnight in pH 4 buffer containing an additional 10 g of KCl for every 100 mL.

In food plants no glass, so the lab is already using ISFET pH electrodes(solid state). We either store them dry for the portables, or in D.I. water for the table top units that are used 3 shifts/day.

[William Rose]

My experience has been that the glass probe should be kept in a pH7 buffered soaking solution (ask supplier). You may want to get some "Parafilm"tm as well, so that you can seal the beaker (typically 50 ml), the probe, and soaking solution from air-born contaminants. You will also need some pH7 and pH4 calibration solutions (typically yellow and red, respectively).When you calibrate the pH meter (see manual) you will want a slope somewhere between 98 and 102.Finally, you'll need electrode solution to top-off the pH probe or to refill it when you can't get the slope into the desired range. Like most jobs, set-up and clean-up are a significant part of the work.

You may want to have a temperature probe as well because the probe is temperature dependent and the readings will have to be adjusted if significantly above or below 20C (68F).

Bonne chance,

- Bill Coloribus gustibus non disputatum

[Borek]

On Sun, 28 Jan 2007 22:37:12 +0100, William Rose wro= te:

Depends on the electrode type - most electrodes sold now (especially to = =

end users outside chemical/research community) have gelled electrolyte =

which can't be replaced, thus electrode after serving for 6-9 months (12= =

at most) have to be thrown away.

See

details.

Borek