[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: dH/TDS

Keith. 

Very good point.  As just pointed out,  You can change osmotic pressure with
things that do not effect conductivity in the least, like sucrose.  a 20 %
sucrose soution in r/o water will have hardly any TDS.  Put a fish in it and
the water will be pulled from tissues, because the osmotic pressure outside is
greater then inside.

On 11-Sep-00 \"Grif\" w. keith griffith wrote:
> 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
>>button.
>>
>>On 11-Sep-00 Wright Huntley wrote:
>> >
>> > I must disagree, here. Killies are dependent on osmotic pressure to 
>> regulate
>> > 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 
>> water
>> > 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 
>>good.
>>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 
>>resistance),
>>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.
>>
>>Peace
>>john
>>----------------------------------
>>E-Mail: listhub at libros_andante.mn.org
>>Date: 11-Sep-00
>>Time: 18:07:33
>>
>>This message was sent by XFMail
>>----------------------------------
>>---------------
>>See http://www.aka.org/AKA/subkillietalk.html to unsubscribe
> 
> 
> 'Grif'   N7IVS
> 
> ---------------
> See http://www.aka.org/AKA/subkillietalk.html to unsubscribe

----------------------------------
E-Mail: listhub at libros_andante.mn.org
Date: 11-Sep-00
Time: 18:44:22

This message was sent by XFMail
----------------------------------
---------------
See http://www.aka.org/AKA/subkillietalk.html to unsubscribe
References: