LaMotte Calcium Hardness Test Kit (1 Viewer)

[DRH]

Does anyone use the subject test kit? I've just switched to using this one and the results are confusing if you read the instructions carefully (at least to me).

The titration is performed on a 1 to 12.9 solution and yields a reading in what is documented as ppm CaCO3 equivalents (after multiplying the resultant by 12.9). Converting to Ca++ should be had by multiplying by .4. I get bizarrely high readings with this kit. I'm thinking that the EDTA that is used as the tritrant is also in solution in my aquarium (it is a chelating agent and I'm quite sure these are used in many additives). Although, I would think this would bias the result down not up.

I guess my questions are:
1) Does anyone know of aquarium additives that contain EDTA?
2) Is anyone with this test kit seeing similar results?

Thanks a bunch!
Darrell

 

[garyandmike]

I use the LaMotte test kit.

My instructions say to multiply the final reading by 5.16 to get Ca reading in ppm. I have never seen anything about multiplying by .4 . It does say to dilute 1ml of seawater to 12.9 ml, but nothing about multiplying by 12.9.

My reading have genererally agreed with those done at Global...
Maybe they have changed it with newer kits..

 

[DRH]

12.9 X .4 = 5.16

Sounds like the new (???) instructions left out some of the details of the computations....

 

[garyandmike]

Gee, aint't math wonderful .....
Anyway, I guess you are still getting high readings.

On my kit it will chnage color from purple to blue, the instructions say to ignore the change back to purple that happens after a short time. Maybe you're overshooting the endpoint???