Salifert KH/ALK profi-test kit question

[kbreese]

I just set up my reef tank last night and just started the protein skimmer today and did a test for ALK with this kit. My question is about where it states that you drop the KH reagent into the vial until the water turns orange-red or pink color. After so many drops it turned to a very light pink hue, than I dropped one more drop and it turned a definite but still very light pink color. I am not sure exactly where to stop. Do they mean as soon as you see any pink or red in the color to stop or to stop when it's a definite pink or a darker pink or?

When It first hinted at a pink hue the top of the black piston in the syringe was at 5.0 which = 8dkh & 2.86 alkalinity which is what seawater is according to the kit. When I dropped one more drop it was 7.7dkh and 2.74 alkalinity. that's where I stopped and where i thought the accurate measurement was.


(for the record it's a 75g tank and there is 65-70lbs LR and various coral's in the tank which were xferred from an established tank that was running about 2 years)

[Randy Holmes-Farley]

As soon as it is mostly pink and not blue, you are done. Don't worry about the intensity of the color, just the shade. It is always a fine idea to note the reading where you think you are at the endpoint, and keep going just to see what happens after a few more drops. When you are at the endpoint of an alkalinity titration, not all that much more happens with a few more drops.

[Cearbhaill]

Is it kosher to put the unused reagent from the syringe back into the bottle or must it be discarded?
I've always discarded it considering it tainted, but if it is still good I'll start saving it.

[kbreese]

Originally posted by Cearbhaill
Is it kosher to put the unused reagent from the syringe back into the bottle or must it be discarded?
I've always discarded it considering it tainted, but if it is still good I'll start saving it.

I squirted the unused reagant back into the bottle myself. I couldn't see any reason why it would now be tainted.

[kbreese]

Originally posted by Randy Holmes-Farley
As soon as it is mostly pink and not blue, you are done. Don't worry about the intensity of the color, just the shade. It is always a fine idea to note the reading where you think you are at the endpoint, and keep going just to see what happens after a few more drops. When you are at the endpoint of an alkalinity titration, not all that much more happens with a few more drops.

Well all the blue in the water dissapeared on the next drop after I intitially saw the pink hue. It was a very light pink but the blue was gone. So I guess i was correct in reading it at this point.

Now my next question would be is 7.7dkh and 2.74 alkalinity low enough that i should add some of the B-Ionice Alkalinity that I have?

[Habib]

So I guess i was correct in reading it at this point.


Yes, sounds OK. The first color change showing a pink or orange color no matter how faint is just perfect.

FWIW each drop is about 0.1 meq/L so a drop more or less is not that much.

[Habib]

Is it kosher to put the unused reagent from the syringe back into the bottle or must it be discarded?


Well it is not Kosher certified. :D

j/k. :)

It is OK to put it back as long as it has not been contaminated and is in the correct bottle. Sometimes people put it back in a wrong bottle.

[kbreese]

Originally posted by kbreese
Now my next question would be is 7.7dkh and 2.74 alkalinity low enough that i should add some of the B-Ionice Alkalinity that I have?

:confused:

[Habib]

7.7 dKH is IMO fine. I personally prefer 8 - 9 dKH.

[Randy Holmes-Farley]

I agree. I usually suggest that folks maintain 7-11 dKH. I guess that I am less of a perfectionist than Habib. :lol:

[Habib]

I guess that I am less of a perfectionist than Habib.

:lol:


NSW has an alkalinity of approx 7 dKH but generally speaking people can make some testing errors or a brand of test kit can be off somewhat and is not unlikely that a 7dKH value can actually be much lower in some cases.

That is one of the reasons for the recommendation I gave. :)

Another reason is that alk can drop quite fast if calcification takes place.

[saltwater-nut]

How about the LaMotte ALK test kit? There doesnt seem to be a referance as to what is recommended.
I'm getting around 110-120 on my syringe reading.
Anyone know a conversion table for this kit?
Thanks

[Habib]

From the following thread it looks like the lamotte uses the ppm CaCO3 unit for alkalinity.

If your version does the same then divide by 50 to obtain meq/L.

So alkalinity as 115 ppm CaCO3 = 2.3 meq/ L


To obtain dKH multiply meq/L by 2.8.

So 2.3 meq/L = 6.44 dKH which is on the low side.



EDIT: Forgot the link to the thread:

http://archive.reefcentral.com/forums/showthread.php?s=&threadid=299243&highlight=lamotte+AND+alkalinity