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Re: Iron test/PMDD

Iron testing can be a problem. I have two Hach test kits.

One test kit will convert Fe+2 to Fe+3.  Then it will change color. The
problem is that you also get a reading of the Fe+3 that is in the water
sample. The Fe+3 is the precipate form of Iron that has been discussed. So
basically, you haven't a clue as to how much of the Fe+2 you have.

Another Hach test kit measures both Fe+2 and Fe+3, but allows you some time
to read the Fe+2 form. If you read it within the first minute, you are
confident of the Fe+2 reading. The problem with that test is that it is
difficult to quantify the small amounts of Fe+2, because of test color
resolution.

Hach explains all of this in the instructions. Most test kit manufacturers
do not. In fact, Hach also supplies standards that you can callibrate to.

The bottom line is that if you don't know what form of iron the test is
testing for (and how it does the test), you simply cannot quantify the
amount of Fe+2 that is in the water.

What has been suggested before is the best method to dose iron: learn to
read the plants, and err on the side of too little. Excess micronutrients
will cause you more grief than too little.
-- 
Augustine Rodriguez
Rice Lake, WI USA

> I have read posts from other folks saying that they needed to leave the
> test brewing overnight to get a good reading. YMMV.