Some handy facts about water

[Hufsa]

As no references apart from a few wikipedia pages are given (apparently the author discovered all himself) it’s hard to say where things broke apart. So just assume failure in copypasta from some uncredited work

I’ll keep my opinion about the rest of the article to myself and leave to the readers and moderators to compare to the standard set by other excellent articles found on this nice forum, such as Ceg’s EI articles published 14 years ago.

This seems unnecessarily harsh, if you have issues with the article why not share them so they can be discussed? Talking about someone in a roundabout way is rarely conducive to a productive discussion

 

[Ria95]

The correct equation is now available so guess that’s a rare case of productivity from my side

 

[palcente]

LOL. Low - high; high -low it’s all bonkers.

=A*0.35665*(10^(6.35-pH))*44

I noticed it looked different to what I've used before. I previously derived a version that also accounts for temperature. I'm not a scientist, so that's not mine, rather stolen from research I found online. And if anyone knows and wants to try and explain to me where it all comes from that would be great. Although I probably won't understand...

 co2 =13.4 * dKH*(10^(pKa-pH))

Where pKa is derived from the following table:

    '''
    > T (C)    pKa
    > 0 6.58
    > 5 6.52
    > 10    6.47
    > 15    6.42
    > 20    6.38
    > 25    6.35
    > 30    6.33
    '''

My complete python code for anyone wondering is this:

def calculatePKa(temperature: float)-> float:
    slope = (6.35 - 6.38) / (25 - 20)
    b = 6.38 - (slope*20)
    output = slope * temperature + b
    return round(output,2)

def co2ppm(dKH: float, pH: float, temperature: float) -> float:
    pKa = calculatePKa(temperature)
    co2 = 13.4 * dKH * (10**(pKa-pH))
    return round(co2,2)

Take it with a grain of salt, but it fits the tables circulating online and so I use it in my dashboard.

Matt

 

[jaypeecee]

Remember I got a MW500 ORP meter a while back

In any event, ORP/TOC are not easy topics.

Hi @MichaelJ

I have just spotted the above thread/posts. You may recall that I also have the Milwaukee MW500. ORP at its heart is very complex. And that's because it's responding to a whole load of oxidation and reduction reactions that are simultaneously taking place in the aquarium water. From numerous measurements, I am of the view that there is a correlation between the ORP value and dissolved organics. I'm not alone in this respect. This topic appears from time to time elsewhere. In one of my tanks, a typical ORP figure is +350 mV but this figure drops as organic waste builds up.

Although the name, Randy Holmes-Farley is better known in reefkeeping circles, he has written a great deal on the topic of ORP/redox. Here's a sample:

https://reefkeeping.com/issues/2003-12/rhf/feature/index.htm

I'll stop there.

JPC