Alkalinity Article

[Randy Holmes-Farley]

My alkalinity article is now posted at AAOM:

http://www.advancedaquarist.com/issues/feb2002/chemistry.htm

It should tell you more than you ever wanted to know about alkalinity.

[Chuck Anderson]

Randy,

Your article is very informative.

I have one question:
You give a link to an Alkalinity Conversion Table. (http://ozreef.org/reference/alkalinity_conversion.html)
Are the highlighted rows on that table the Ideal range for Alkalinity?

TIA

[Randy Holmes-Farley]

Chuck:

Your article is very informative.

Thanks! :)

Are the highlighted rows on that table the Ideal range for Alkalinity?

Presumably in someone's opinion, but not in mine. I almost said something about that in the article, but then decided not to. The range is way too high.

IMO the "desirable" range ought to include 2.5 meq/L at the bottom (after all, why isn't natural seawater desirable?) and not much higher than 4 meq/L at the top.

[piercho]

OK, from your article I'm going to say that the contents of my test bottle are dilute hydrochloric acid (that's what the bottle says) and bromcresol green (the bottle doesn't say, but it turns from blue to yellow).
The test is in 0.5 meq/l increments, I think. I'd like to test at about 0.1 meq/l increments so I can actually see how much variation I get over a day. I could extend the chart and use 5 times as much water, i guess, if i assume a linear relationship from point to point. But then the little test bottle would only last a few tests.
So my first question is, how can I best go about accomplishing this (measuring to 0.1 increments). The second question is, where can I buy test solutions in volumes more suitable for frequent and accurate testing.
I've been switching over from all ESV to CaOH2 plus ESV to make up the difference. Also, I'm trying to run the tank closer to natural levels of TA (2.7, right?) without going under. This is my reason for wanting to test more accurately at this time.
Thanks for your help, and thanks for your chemistry articles. I'm finding as many reefers pull chemistry "facts" from their rears as pull electricity "facts" from same. Only when it comes to chemistry I've been mostly at their mercy (please don't ask me to dust off that college chemistry text I suffered through).

[Randy Holmes-Farley]

So my first question is, how can I best go about accomplishing this (measuring to 0.1 increments).

The best way would be to get a kit that read much more precisely. The LaMotte and Hach kits are much more precise.

A way that you might try would be to dilute the acid by 5. That is, add 1 part of the acid to 4 parts RO/DI water. Then try the titration as normal. If you can see the endpoint OK, then you have upped the precision by a factor of 5.

<< The second question is, where can I buy test solutions in volumes more suitable for frequent and accurate testing. >>

Many test kits sell refills. That's what I'd get.

[DJREEF]

Thanx Randy - good article. Definitely clears up a number of concepts that the industry has twisted up for us.

In your last paragraph you stated that the test kits using the German standard were actually measuring total alk, as opposed to only carbonate alk, exclusively. I use the Tetra brand test kit with the single titration that measures in dKH ( I'm assuming that this is the kit you're referring to ). So, this kit reads more than just the carbonate hardness stated on the package picking up other species of alk which may not necessarily benefit the system. Just wanted to be clear. Thanx ahead.

DJ
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[Randy Holmes-Farley]

DJ:

So, this kit reads more than just the carbonate hardness stated on the package picking up other species of alk which may not necessarily benefit the system. Just wanted to be clear

I'm not familiar with that kit, but if it is a simple single titration, yes, it picks up everything.

[DJREEF]

That it is. Thanx Randy.

DJ
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