LaMotte test kit warning
I finally broke down and got a LaMotte test kit, an Alkalinity test to determine Carbonate Hardness. With CO2 calc's being so critical (if you are pushing it to high numbers), having solid numbers around dKH seemed essential.
I'm happy with the kit overall... the results are quite precise. And I hope reasonably accurate. You can detect in increments of about 1/4 of a degree KH, or smaller. But you do have to really look hard to see the color change when the reagents hit their endpoint. But if you look hard, in good light, you can indeed see it.
But I'm posting this as a warning to other people with this same kit. Or for all I know, this could be a problem with all LaMottes's.
The kit comes with a glass vial to hold the sample to be tested, as do most kits. And like other kits, it's marked on the side with significant gradations in milliliters. But in the case of my kit, the markings appear to be wrong.
You are supposed to test with 5 ml of sample water. And as far as I can tell, 5 ml goes way above the 5 ml line on the supplied vial. Using a dosing syringe to measure out 5 ml, I filled a vial from a Red Sea kit. Then I repeated the process with a vial from an AP test kit. And again with the LaMotte kit vial. In every vial but the LaMotte, the gradations on the vial showed 5 ml of sample water. In the LaMotte it was well above 5 ml. When I used the dosing syringe to remove water until the LaMotte vial read on the 5 ml mark, I removed 0.7 ml.
In all of these cases, I'm reading the bottom of the little curve the water makes in the vial. I believe I remember that from high school chemistry.
But regardless, the AP vial, the Red Sea vial, and the dosing syringe all agree. I'm afraid the LaMotte, while expensive and potentially accurate, is badly flawed in the marking of their vial - which will significantly throw off test results. If I'm doing the math right, it looks like this might produce reading about 15% lower than it should. Not what you would expect from such a kit.
So I'm tossing this out there as a word to the wise. Be aware.
Steve - 33g reef and a 180g planted in need of a re-scape.