gH and kH testing: what do you think of this idea?

[juggler]

For testing gH and kH, normally they advise starting with 5 ml test water and then you drop the test liquid until colour changes. I find this may be wasting the test kit if your kH or gH is generally high.

What if we start with 1/2 the amount of test water, say 2.5ml, and then starting dropping the test liquid? And then mulitply the result by 2?

Will this be accurate? If ok, that means can double the life of your test kit. I have not tried it yet.

[kingpin]

Koah Fong,

I remembered the JBL test kit instructed using 10 ml, instead of the usual 5ml of tank water to measure up to 0.5 degree in Kh. It should be the same, that is 2 degree corresponding to every drop if 2.5ml is used.

[zmzfam]

testing is just another form of sampling. similar to a survey, if u want greater accuracy, u would survey as many people as possible. likewise, if u use double the amount of water, the results would be more accurate.

in the case of high kH and gH, maybe it is worthwhile since u use less reagent and u do not need that high an accuracy. But for a planted tank where u normally maintain a kH of 4-6, it shouldn't make any difference?

[FC]

"What if we start with 1/2 the amount of test water, say 2.5ml, and then starting dropping the test liquid? And then mulitply the result by 2?quot;

Yes, it works too but the margin of error will be increased unless you can get the 2.5 ml right. One way is to use test tube that has small diameter and long tube. The AP brand test kits provide that. The other problem is the readings will be in even numbers, that's accuracy is limited to the nearest even numbers.

[geoffrey]

I would think you need to add 2.5ml of distilled water to the 2.5ml of tank water before test. That will dilute concentration by half hence multiply by 2 after titration.

[juggler]

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On 5/6/2003 8:45:50 AM

"What if we start with 1/2 the amount of test water, say 2.5ml, and then starting dropping the test liquid? And then mulitply the result by 2?amp;amp;quot;

Yes, it works too but the margin of error will be increased unless you can get the 2.5 ml right. One way is to use test tube that has small diameter and long tube. The AP brand test kits provide that. The other problem is the readings will be in even numbers, that's accuracy is limited to the nearest even numbers.
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Mmmm... even numbers?
Then I should dilute 5ml tank water with distilled water to 15ml. Then take 5ml of the sample to test. Multiply result by 3. This can solve the even and odd readings.
And I can triple the lifespan of the test kit. []

Just a thought.