10ml

Syntax1235 · Jan 3, 2019

I was having a discussion with a science teacher I work with regarding on how to read the 10ml line on the alk checker. He mentioned that some test tubes are meant to be filled so the water level at the bottom of the curve is at the line, others when the top of the curve is at the line. When exactly is there 10ml in the vial?

I’ve tried a couple 10 ml syringes and they seem to put too much water in the vial.

Gareth elliott · Jan 3, 2019

I always fill the bottom curve to the line. This way the test is always preformed the same each time. My main care for an alkalinity test is that the variation from my last test matches my plan to compensate usage.
Honestly dont care if my tank is 8.3 or 8.4 only that whatever it is, is stable at that number.

miPapareef · Jan 3, 2019

I’ve only ever know the meniscus arc to sit at the top edge of the line.
https://en.m.wikipedia.org/wiki/Meniscus_(liquid)

Swingline77 · Jan 3, 2019

It's accepted to read to the middle of the line, though doing so is irrelevant in this case.

There is some amount of error in all graduated cylinders. If you were to take ten graduated cylinders made by ten different manufacturers and fill them to the same marking relative to each other, you'd probably have variation in volume of a few tenths of a milliliter.

When you want to measure "10 ml", how accurate do you want to be? Would 9.8-10.2 ml be considered "10"? What about 9.95-10.05? 9.995-10.005? You get the idea. If 9.8-10.2 is sufficient, I'm sure what you have is sufficient. Use it to measure to the top, middle, or bottom of the line. The volume variation will be minimal. If you want to be more precise, you can use a "volumetric flask" (https://www.ebay.com/itm/5-10-25-50...148ba1165:m:mUmhxGn6Mw6CRx0MZId-wTw:rk:1:pf:0)

As Gareth said, I don't think that you have to measure things that exactingly. Consistency is probably more important. Just pick either the top, middle, or bottom of the line and consistently measure to that location.

rcpalmer1 · Jan 3, 2019

I was very concerned when I started using the hanna checker. I was worried when I noticed they changed the syringe. At RAP I talked with one of their lab people. He told me that with the dilution rate it was not that critacal. I tried testing with water above and below the line. I was surprised that I would get the same result. As same above just try to do it the same every time. I test my tank almost daily, 9 times out of 10 it is what I expect it to be. I never make changes based on one test.