alk and elos problem

[tosiek]

I just went through 3 elos test kits, one older and 2 of the newer ones and all have shown bad KH readings. I tested against a salifert and tested all the kits against a 7.4 KH check solution. The salifert and the second Elos showed a 7.4 +/- .02 while the other two showed high and low on the 7.4 checker solution. But that second Elos test kit didn't show what the salifert showed on my tank water. It kept reading a 5.5 or 6.5.

I'm at a loss. Im going with the salifert for now which is where my range feels like it is at around 9. PH and Calc are on spot at 8.0-8.3 and 430. Mag is a bit low at 1250 but that shouldn't affect a reading on my KH.

Anyways, super frustrating both while trying to tune my litermeter in and my pocket.

 

[Boomer]

Tosiek

Measuring Alk is not an east task and is often user error. One needs to be exact on the instructions. Salifert usually reads high, as they are suppose to, as many Alk kits are not set for sewater and its lower titration pH. Two people using the same kit and running the same sample will often come up with different reading's.

 

[KathyC]

If I may slightly hijack...then what is the best way to get a proper alk reading..run the test twice and if the results don't match, should a person average the two.
Or should 2 different type kits be used?

Also - how do you use that 7.4 check solution now included in the Salifert Alk kits? I saw no directions included on HOW to do it?
Shouldn't that insure that testing results are spot on??

 

[tentacles]

wondering about the check solution as well.

 

[finksmart]

I believe you draw 4ml of the check solution as you would your tank water to confirm the accuracy of the test kit. Not used for normal testing.

 

[Boomer]

Kathy

First per finksmart.

Second:
then what is the best way to get a proper alk reading..run the test twice and if the results don't match, should a person average the two.
Or should 2 different type kits be used?

Yes run the test twice, on the same kit and do an avg and DO NOT get stuck on "I want my Alk at 11 dKH". Pick a range, like 10 -12 dKH and if you are in that range leave it alone. Proper means of Alk, which most will never do, is lab tritration for seawater using a pH meter. Test kits are somewhat of a poor method with to much to go wrong by the user or the kit itself. Basically, there are just close enough. We are never going to know what kit is what until they are sent to a real lab for verification. Habib (owner of Salifert), has sent his to Millero babs for verification, the best place on this planet IMHO. For all other kits, except the Sailfert, till proven otherwise, I would take all other Alk kit readings and add 10 %. So, if it reads 10 dKH, then it is 11 dKH. So, where does this 10 % come from ? Most kits are FW kits and do not go to a low enough pH for seawater Alk.

Seawater Alk Determination
http://rutchem.rutgers.edu/sites/chem.rutgers.edu/files/coursefiles/courses_sp11/251/chem_251_exp_2_alkalinity_of_seawater.pdf

 

[Boomer]

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