Question about reported natural black water parameters

[koty]

In several of the reports on the water tested at some black water habitats they report on very low conductivity (around 10 microS, for example) yet a very low pH (around 4.0).
The low pH means three orders of magnitude higher (than neutral) H+ (protons) conentration.
My question is: How can you get such low conductivity combined with such low pH?

 

[five]

I got the tap water go though the DI unit and filtered though peat (Sera) and the result is PH4.3 and ms around 10 or less. Is this good enough?

 

[koty]

Dont get me wrong. I am not questioning the validity of the info. Rather I am trying to understand how the conductivity remain that low.
Now I think that it is possible that as opposed to charged ions (salts), dissolved carbons (from the peat) actually reduce the conductivity values of the water.
koty

 

[Apistomaster]

Hi Koty,
I make no claim to be an expert in chemistry but as I understand it, the low conductivity is not at odds with a low pH at all. It is a matter of the very low TDS which is just the flipside of low conductivity. The low pH is as you described, the ratio of the charged ions of the water molecules. Lacking KH for buffering allows the pH to "freefall" especially in RO or rainwater that has been peat filtered and contains the mild organic acids contained in peat.
Larry W.

 

[DH247]

Basically for conductivity you need to have positivley charged particles and negatively charged particles. What happens in a cell reaction, essentially, is that the negative ions will react with the positive terminal and the negative ions will react with the positive terminal. This causes a migration of the charged particles across the medium and an associated current (defined as the flow of charge). This is why saltwater is more conductive. Because you have Na(+) and Cl(-) ions present that will react with metals put in the water, causing a cell reaction - like a battery.

pH is a logarithmic scale that is a measure of the excess amount of H(+) or OH(-) ions. So, at low pH there is an excess of H(+) ions that have nothing to bond to but to steal OH(-) pairs from other H atoms. In other words the H(+) ion will steal the OH(-) from another molecule of H2O. When the pH is 7, neutrality, there are no excess H(+) nor excess OH(-) ions. So all the molecules (on average, chemically speaking :wink: ) are H2O. When above pH7up to 14, there is an excess of OH(-) ions present.

In either case, when TDS are very low there are no other ions present to cause any kind of reaction, hence there is no flow charge giving a very low conductivity reading.

I hope that makes sense. Anyhow, I have to go write a calculus final. Oh joy of joys :frown:.... If you have q's please let me know and I'll pull out my chem book to double check!! :biggrin:

 

[five]

Hey koty, apologies for misinterpreting your message.

Thanks DH247. Such a confusing topic, at least to me :redface: , you made it sounds so simple.

 

[tjudy]

Although H+ is technically a charged ion, it is not very conductive. A conductivity meter is measuring the dissassociated salt ions (TDS), such as Na+, K+, and Cl-.