Problem with Hanna alk reagent

[Koigula]

Copy from my answer in another thread





Sincerely Lasse

Thanks for sharing this. I saw a few bugs fungi/mold cooking in hanna reagent vial so tend to agree.

 

[ceaver]

Copy from my answer in another thread





Sincerely Lasse

+1 that the issue is reagent slowly going bad over time after it's been opened. The Hanna pH reagent has the same issue. I did not know about refrigeration as a way to address this, great information!

 

[Koigula]

my $0.02
The most simple and fundamental measurement of Alk is a titration. It's absurdly repeatable.
That hanna was able to use a reaction to produce a linear color change for alkalinity level has always seemed to me like one of those things that shouldn't work. So I'm impressed that it kinda does.
I love hanna kits but I don't and wouldn't use their alk checker, because I'd like to be able to drill down and get more precise alk than what that method can allow. Even their claimed uncertainty for the alk test is notably higher than their other tests.

Did you ever define a test with indicator and tritrant or do you just use an alternate test kit?

Something like 0.1N sulfuric acid to endpoint with phenolphthalein end point pink to clear and methyl orange end point yellow to red. If not sure no problem. This is testing two semester from '91 for me that I never really used...

https://www.colby.edu/reload/chemistry/CH331/CH331Limit/2320-Alkalinity.pdf

https://www.reef2reef.com/ams/a-diy-alkalinity-test.12/
An indicator solution would be much easier if possible. Using 250 cc sample would be way more accurate

https://sg.vwr.com/store/product/29...itration-of-first-hydrogen-of-phosphoric-acid

 

[Randy Holmes-Farley Verified Community Expert]

Did you ever define a test with indicator and tritrant or do you just use an alternate test kit?

Something like 0.1N sulfuric acid to endpoint with phenolphthalein end point pink to clear and methyl orange end point yellow to red. If not sure no problem. This is testing two semester from '91 for me that I never really used...

https://www.colby.edu/reload/chemistry/CH331/CH331Limit/2320-Alkalinity.pdf

https://www.reef2reef.com/ams/a-diy-alkalinity-test.12/
An indicator solution would be much easier if possible. Using 250 cc sample would be way more accurate

https://sg.vwr.com/store/product/29...itration-of-first-hydrogen-of-phosphoric-acid

I show a DIY alk titration here. IMO, if you use a standard acid, it is more accurate than a kit for the reason you suggest: large sample volume.

A DIY Alkalinity Test: By Randy Holmes-Farley - REEFEDITION

Alkalinity is one of the most important measurements that a reef aquarist can make. It can become rapidly depleted in many aquaria, requiring frequent measurement in order to maintain stable levels.

www.reefedition.com

 

[taricha]

Did you ever define a test with indicator and tritrant or do you just use an alternate test kit?

I use Randy's DIY method linked above, or Red Sea kit, if I don't have a calibrated pH meter handy.

 

[shadyraro]

My KH keeper plus was reading 8.9 so I wanted to double check it with my Hanna and salifert.
My Hanna gave a lower reading so I thought the reagant was off, so I got a new bottle of reagant and got the exact same result. Then I tested with a new salifert kit and it read exactly the same as my KH keeper.

Results
Hanna old reagant 8.5
Hanna new reagant 8.5
Kh keeper plus 8.92
Salifert 8.9

So what reading is correct?

 

[nereefpat]

My KH keeper plus was reading 8.9 so I wanted to double check it with my Hanna and salifert.
My Hanna gave a lower reading so I thought the reagant was off, so I got a new bottle of reagant and got the exact same result. Then I tested with a new salifert kit and it read exactly the same as my KH keeper.

Results
Hanna old reagant 8.5
Hanna new reagant 8.5
Kh keeper plus 8.92
Salifert 8.9

So what reading is correct?

Those are close enough to call them the same.

Gun to my head, I would trust a titration over a Hanna checker, since alkalinity is a titration by definition

 

[shadyraro]

Those are close enough to call them the same.

Gun to my head, I would trust a titration over a Hanna checker, since alkalinity is a titration by definition

Yeah I agree, I’d trust the salifert and KH keeper over the Hanna