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ricwilli

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I just ran alk tests with the Hanna kit and Salifert kit. The Salifert kit came with a Alkalinity Check Solution 8.1 dkh +/- 0.3.

- Hanna 134ppm
- Salifert 9.3dkh
- I tested the Salifert with the "Alkalinity Check Solution" and got 8.32dkh

So what reading should I be going with? I just got the checker and tested twice as well with the Salifert.
 

Breakin Newz

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Hard to say, if you want to bring your water over one day real quick ill check it with my elos kit to compare to your other kits...

Sent from my ADR6300 using Reefs
 

radiata

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Nice article...

Who is "Pomacanthus Publications, Inc."?

How much of a possibility is it "to establish a correction (and comfort) factor to apply to the Hanna Checker's results"?
 

Boomer

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So one does not get lost here as there are some issues with the article.


What is Alkalinity
http://www.advancedaquarist.com/2002/2/chemistry

From it:

The precise endpoint of a total alkalinity titration isn't always the same pH, but rather depends a bit on the nature of the sample (both its ionic strength and its alkalinity). For normal seawater, this endpoint is about pH = 4.2. In freshwater it depends strongly on the alkalinity, with an endpoint of pH = 4.5 for an alkalinity of 2.2 meq/L, and pH = 5.2 for an alkalinity of 0.1 meq/L.


Well, the Hach kit was designed for use in fresh water where the pKa of the bicarbonate is much higher than in seawater, and in that situation, it is appropriate. In seawater, however, it is marginal. My tank water took 3.4 meq/L to get down to pH = 5.03, and then an additional 0.4 meq/L to get down to pH 4.00. Consequently, this kit (and others with a similar dye mix) may be missing out on 10% of the alkalinity simply because it isn't titrating low enough. This difference obviously isn't significant to most reef keepers, but is something to keep in mind when doing such things as comparing test kits to standards (in seawater) or to each other.


Lets look at the plot of 180 ppm for the HACH vs Hanna 240 ppm

So now we need to add 10 % to that HACH reading of 180 = 198

Now the Hanna is reading 18 % to high.

HACH = 198 ppm

Hanna = 240 ppm

240 ppmx 18 % = 43 ppm and 240 ppm - 43 ppm = 198 ppm



Hanna reading - 18 % at ~normal pH and Alk = a more true Alk.
 

radiata

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Boomer,

So you're comfortable with subtracting 18% from the Hanna reading, when the pH is normal, to get a reasonably accurate Alk reading? If so, what is your normal pH range, and is your normal pH range with electronic or colorimetric testing gear? (I find great differences between electronic and colorimetric pH readings.)

Thanks in advance,
Bob
 

Boomer

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Bob, so sorry I'm so late to rely :(

There is more to the story after re-looking at Dana's article and talking to a Habib and Chris. I guess I forgot to post it here. :(

Guys I spent allot of time with Habib from Salifert and we are not out of the water yet, so will reply here more soon. I l also talked to Chris Jury about it. This whole Hanna and test done by my friend Dana seems to be a big mess. It appears the Salifert is right on and does read higher than the Hanna and is suppsoe to. That means the Hanna is more accurate than the HACH test done in the article. In Alk testing there is a serious issue between CO2 in FW and CO2 in SW. Also, the titration end point is not the same at high Alk as it is low Alk. I looked at Millero Labs (the only place to test a Alk kit for seawater) data sheets on the testing of the it and it is +/- 0.1 dKH within NSW on his reagents. I will try to get Habib to reply to this thread. He is thinking of doing a full blown article for Advanced Aquarist to clear up all this Alk mess we have always had to deal with. I have said for years the Sailfert is the best Alk test and it now seems to being proved me right again but have had my doubts from posted Salifert values and Dana's article. I too have been led astray.

This is who Dr. Frank Millero is

http://cdiac.ornl.gov/oceans/

http://www.rsmas.miami.edu/people/faculty-index/?p=frank-millero

http://www.amazon.com/dp/0849384230/?tag=reefs04-20
 

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