Lamotte's explananition of Alkalinity(it's a good one)

Tom Barr

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Below is a comment on Alkalinity which most aquarist attribute to entirely KH, bicarbonate. This is not the case for many tap water supplies however.
Perhaps you might get lucky and it is all bicarbonate???:confused:


How do you know?
Have you tested for the other forms and measured total vs bicarbonate?
If not, then you cannot say, you can guess.....but you cannot say or confirm it.



"CALCULATION OF ALKALINITY RELATIONSHIPS
Results obtained from Phenolphthalein and Total Alkalinity
determinations offer a means for the stoichiometric classification of
three principal forms of Alkalinity present in many water supplies.
Classification attributes the entire alkalinity to bicarbonate, silica,
phosphoric and boric acids. This classification system further assumes
incompatilibity of Hydroxide and Bicarbonate Alkalinities in the same
sample.

Since calculations are on a stoichiometric basis, ion concentrations in the strictest sense are not represented in the results.

According to this scheme:
A. Carbonate Alkalinity is present when Phenolphthalein is not zero
but is less than the Total Alkalinity.
B. Hydroxide Alkalinity is present if Phenolphthalein Alkalinity is
more than one-half the Total Alkalinity.
C. Bicarbonate Alkalinity is present if Phenolphthalein Alkalinity is
less than one-half the Total Alkalinity."

http://www.lamotte.com/pages/common/pdf/instruct/3467.pdf


Regards,
Tom Barr
 

pepetj

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Interesting article. What is expected in terms of dKH readings (titration method) in soft/acidic water (obtained by CO2 injection in RO processed water with added sodium bicarbonate and Seachem's Equilibrium).

Is it reasonable to take a 0.5 or 1.0 dKH reading as truly [bi]carbonate hardness? Or would you expect Hydroxide alkalinity to be significant? What would this mean in terms of fishkeeping in planted tanks?

Any idea what the reagents are?

Santo Domingo
 
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Tom Barr

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Hard to say for any specific tap water really, they might add PO4, there might be more hydroxide........depends.
Some folks get lucky, others do not.

PO4 is often added for corrosion control.

A good test to measure each type would be nicer.

Tom Barr
 

Biollante

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Hach To The Rescue...

Hi,

I am not familiar with Lamottes testing but it appears similar to Hach's and from the Phenolphthalein alkalinity test; carbonate, bicarbonate and hydroxide alkalinity are easily derived... :)

Hydroxide, usually either potassium hydroxide or sodium hydroxide are used to protect from corrosion. Though as it is a flocculant most of it should end up in the sludge. :gw

In the pH ranges of our freshwater aquaria I would not think this much of an issue. :) My sampling and knowledge is too limited to make general statements, if I have misunderstood the point of this thread, I apologize. :eek:

A little general information http://www.wqa.org/glossary.cfm?gl=663.

For those wishing to calculate akalinity http://or.water.usgs.gov/alk/methods.html, http://www.cdph.ca.gov/certlic/drinkingwater/Documents/Drinkingwaterlabs/AlkalinityConversions.pdf, http://water.usgs.gov/owq/FieldManual/Chapter6/section6.6/html/section6.6.5.htm#665A, http://www.norweco.com/html/lab/test_methods/2320bfp.htm and http://comp.uark.edu/~ksteele/hc2004/ALKALINITY- CALCULATION.htm.

Biollante
 

Tug

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Will any of this make it's way into the book? Two or three years from now I might be able to understand what you all are talking about.

Thanks for the links.
 

Tom Barr

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KH is not as simple as many have often assumed, but there are ways to measure it, it's just few hobbyists will ever do it much.
Changing this and attitudes, assumptions about what they think they know about alkalinity and CO2 will take a VERY long time I'm afraid.

Regards,
Tom Barr
 

Oreo

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Keep in mind too that for those on municipal water service alkalinity (total & carbonate) changes daily. How broad the swings are from day to day will depend on the water source. For instance, ground water (wells) tend to be fairly stable over the short / medium term but surface water (streams & lakes) change with the weather, literally. If you call your water provider they can give you some information about what the water source is and what their alkalinity tests have been recently. You'll still want to test the water going directly into your aquarium frequently to verify, especially if you intend to calculate CO2 that way.
 

pepetj

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I figure it's safe to assume that those of us using only RO processed water (say TDS < 20ppm) with added Seachem's Equilibrium and sodium bicarbonate to mostly have a Phenolphtaleine Alkalinity that is (more likely than not) noticeably less then half the Total Alkalinity. This would mean that our total alkalinity should be of the carbonate and bicarbonate types and should remain that way unless tap water enters the aquarium.

Is my assumption right?

Pepetj
Santo Domingo
 

Tom Barr

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Yep,

But IME, 30ppm might not be enough for most light PAR RANGES.
I use 50-80ppm in my tanks.
20-30ppm is not enough to give decent results.

Regards,
Tom Barr