Re: [Killietalk] TDS vs. Conductivity

[Barry Cooper <bjc3 at centurytel_net>]

Well, Charles is correct and is saying, really, the same thing as Lee 
and I. TDS is really every thing dissolved in the water, except for 
gases and other liquids like alcohol, a popular solute, but not a solid  
;-) . Charles is correct in saying that you have to evaporate the water 
to measure the TDS. those include both conductive and non-conductive 
substances (with regard to a current). It is unfortunate that TDS has 
been adopted to express the amount of ionized salts in the water.

Having said that, there is a purist view and a practical view. TDS can 
give you some useful information, but you need to understand its 
limitations. I will repeat, if you really want to know what's going on 
in your water, get a proper analysis.

Why do we focus on certain things? Because they are common, present in 
relatively large concentrations, and because we can readily measure 
them, with kits and so on. One shouldn't overlook though, the importance 
of trace minerals etc. That's one of the reasons I like to use some 
Equlibrium in my very soft water. It adds some important trace minerals, 
such as magnesium, manganese, cobalt, copper, iron, and so on. Many of 
these, like copper, are toxic in large amounts but are absolutely 
essential in trace amounts. The only difference between a beneficial 
compound (or a medication) and a harmful one (or a toxin) is the amount 
you take in. In a prior life, when I was a pharmacist, we even used to 
put HCN (cyanide) in some medicines.

Barry

Barry J. Cooper
Sweet Home, OR 97386



Markus Brown wrote:

>Charles..
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>
>
>You point out a relevant and logical explanation. However, to create 
>dialogue of better understanding to our hobby, the description of variable 
>water properties recently described on Killitalk is more of a value to the 
>"Aquarist" than perhaps your textbook definition. It is important to know 
>the basic definition of the terminology we through around here, but I try to 
>remember, some of us, myself included, like to here the arguments for and 
>against the use of conductivity/TDS. I find it fascinating that there can be 
>so many variables toward water quality and we tend to focus on so few of 
>them in common conversation. Thank you Lee and Barry for the terrific aqua 
>chatter!
>
>
>  
>
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>
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