understanding water for your reef

[curator]

Did you ever wonder what’s in the water.

How a conductivity Meter Measures Salinity.

Did you ever wonder what is a conductivity meter exactly measuring in the tap water, or our freshly mixed salt water. When most of us think of conductive materials, we think of heavy metals like iron, copper and such. Salt (NaCI ) when dissolved in water forms electrolytes. Most of these become ions(a corpuscle that conducts electricity). (Na+) and chlorine (CI-) each of which has the capacity to conduct. Measuring Conductivity is an index of the ease of electricity to flow through water, so the more salt in the water the higher the conductivity, because of its increased potential to carry a charge. Consequently the same conductivity meter helps us determine the purity of our make up water. If you are processing your water though a RO / DI you may get a reading or 5 - /2k microsiemens which tells you the water in near pure. Now you may find yourself asking what a TDS (total dissolved solids) meter will measure, and what is the difference between a TDS an Conductivity Meter, I’d say consult the manufacturer. To understand the entire picture of water, you can benefit from studying and comparing the measurements from either meter over and observed time frame, since the tap water from sources like this city is not constant.

Blane

 

[randy holmes-farley]

As I replied on another board, I disagree with your assertion that TDS meters (a repackaged conductivity meter) can measure anything but electrolytes. TDS and conductivity meters do exactly the same thing, though sometimes in different conductivity ranges, and neither can detect any nonelectrolytes.

For those interested in how a conductivity meter can be used to measure salinity (a very good way, btw), this article details it:

http://www.animalnetwork.com/fish/libra ... ordNo=1300

 

[O P Ing]

hi.
When sugar dissolved, is it still a "solid?" --- asked by a freshman in a chemistry class.

 

[randy holmes-farley]

No, it is not a solid. But it would qualify as a dissolved solid. Nevertheless, TDS (Total Dissolved Solids) meters will not detect pure sucrose when dissolved in water because it is not charged and hence cannot carry any current.

 

[O P Ing]

hi.
I know, but your post just remind me of some old memories.

Do you know what is the molar refractivity of surcose and other common non-electrolytes? (Don't have the CRC reference handy...) Maybe refractometer can be used for this purpose if conductivity measurement is not applicable.

 

[randy holmes-farley]

Refractometers and hydrometers are perfect (and widely used) for sugar solutions. I have a table of refractive index and density of sugar solutions, but neither is useful as a technique below about 0.5% by weight (0.015 M). So for low concentrations, some more sophisticated technique will be necessary.

 

[O P Ing]

hi.
Iodine is widely used as a colorimetric technique for sugar, but how practical it is I have no idea. I also remember something called Fisher's Reagent for sugar analysis, but I have not touch these stuffs for a long time. I feel we are getting off topic here :wink:

 

[randy holmes-farley]

We use iodine for some starch analyses, but yes, that is quite off topic.

 

[O P Ing]

hi.
Did I said sugar? oops...