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Not sure how much this has to do with the real world of real water holding
fish in a sort of closed system,,, but just plain old table sugar will
cause major osmotic pressure changes, and, (30 year old info+etoh+brain)
will not affect the conductivity or ph at all.
How many important non-ionic compounts are present in hi enough
concentrations to cause measurable osmotic changes with few or no
conductivity or ph changes? Guessing that the issue is not a big one, or
I'd have seen comments over time in the press.
At 06:27 PM 9/11/00 -0500, you wrote:
>Those turned off by Physical Chemistry of water solutions, hit the delete
>On 11-Sep-00 Wright Huntley wrote:
> > I must disagree, here. Killies are dependent on osmotic pressure to
> > the amount and salinity of bodily fluids, just like any other fresh-water
> > fish. Conductivity, which we measure as tds, is very closely linked to the
> > osmotic pressure across the cell membranes in such fish. Sudden changes in
> > it are what gave rise to all the old "pH shock" myths.
> > The jury is still out on the effect of the hardness ions (divalent metals
> > like Ca, Mg, Fe, etc.) on rain-forest killifish egg development. There is
> > little dispute of the fact that suddenly dunking a killy from high tds
> > into RO or DI will damage gills and usually kill it dead.
>All ions contribute to TDS. Ca++ Mg++ Fe++ contribute the same as Na+ or K+.
>In fact the movement of an electron through a solution of any substance is
>dependent on the facility of the electron to enter the outer orbital shell of
>whatever positive ion is available, often referred to as "solution resistance"
>TDS is a measure of this conductivity.
>Osmotic pressure is the difference between ion concentration on one side of a
>membrane (or piece of dialysis tubing) and the other.
>TDS is no better measure of that difference then something which actually
>measures ion concentration in a different manner. In fact, it is not as
>If you take a solution of Fe++ that has a relatively low delta between the
>outer orbitals that the electron will enter and leave (low solution
>this solution will have a very high TDS (conductivity) for a very low ion
>concentration (osmotic pressure). If you use Na+, high resistance to electron
>flow, to achieve the same TDS as the Fe++ solution you must have a higher
>concentration of Na+ ions resulting in a higher osmotic pressure.
>Your statement that osmotic pressure is is necessary to regulate body fluid
>levels is important is cure. Using a TDS meter vs a solid measurement of dH
>(GH) is what I question. I have been spawning discus for 20 years and never
>gave a #$@% about micro-Siemens. I know what my GH, KH, and pH are. I don't
>worry about conductivity.
>Is measuring conductivity a good thing, yes. But IMHO not as important (or as
>cheap to measure) as the other three.
>E-Mail: listhub at libros_andante.mn.org
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- Re: dH/TDS
- From: Wright Huntley <huntley1 at home_com>
- Re: dH/TDS
- From: listhub at libros_andante.mn.org