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pH Meter Tests

Our potting mixture is too deeply colored to get a pH reading from a regular garden soil test kit, so we bought a pH meter – actually a Moist/Light/pH meter.

The extremely low germination rate and sickly behavior of seedlings made us suspect the soil pH.  So we tested the pH meter.

Testing tap water, the meter reads pH 6.7 with an inch immersed and pH 5.2 with four inches immersed.  Our regular garden soil test kit yields a pH of 7 for our tap water.

We were unable to attain deep immersion in a compartmented potting tray, so we filled a jar with potting soil and added water.  The meter read ph 5 with an inch immersed and initially pH 3 with four inches immersed.  After a few minutes the four-inch reading dropped to pH 4.5.  There may be pH changes as the various components of the potting mixture react with the water.

We removed potting mixture from several cells of the potting tray and arranged it so as to be able to test at various immersions.  At one inch the meter read pH 6.2 and at four inches the meter read 5.2.

Testing tonic water, the meter read pH 5 with an inch immersed and pH 3.5 with four inches immersed.  The pH changes steadily as immersion increases.  Clearly the pH meter has insufficient impedance.  We tried dissolving various quantities of table salt in the tonic water but there was little change in the readings.

We tried testing the tonic water with our regular garden soil test kit.  The pink solution and buff precipitate don’t match any standard reading so we don’t know precisely how acid the tonic water is.

I wish I could tell you the brand name of our Moist/Light/pH meter but all it says is “Made in China”.  It is green and has two probes.  And the pH function is garbage.

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