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Re: Aquatic Plants Digest V3 #1068

Hello Tom,

You just had to pick a question that does NOT have a clear cut answer!
:-))

The *saturation* point is when no more of a substance dissolves, or
rather when the substance in solution is in an equilibrium with the
solid phase, out of solution.

The *solubility* of calcium carbonate [CaCO3] in *pure* water is only
about 17 ppm (i.e. about 1 "German degree"). It is a well known fact,
that calcium BIcarbonate [Ca(HCO3)2] is much more soluble in water than
calcium carbonate. Calcium bicarbonate is unstable, exists only in
solution, one can not isolate it & put in a bottle. The way one prepares
it, is to add CO2 to the water which is in contact with excess solid
CaCO3. The CO2 (actually carbonic acid, H2CO3) reacts with the calcium
carbonate in solution, forming the bicarbonate, and shifts the
equilibrium, allowing more solid calcium carbonate to dissolve... and so
on. 

If enough CO2 is present, a lot of CaCO3 can dissolve. My well water has
430 ppm CaCO3 hardness. I have heard of places with REALLY hard water
("liquid rock") with over 1,000 ppm CaCO3. So, depending upon available
CO2, the calcium concentration will vary.

Most solid-liquid reactions are slow. In an aquarium with fish one does
not want to change the water parameters rapidly -- it puts stress on
fish, might even kill them. So, a slow coming to equilibrium, in my
book, is an advantage: Just place some marble chips (in a sock) in your
filter, and forget about it for several days. Take out the sock when you
reach the target hardness -- that's all there is to it!

Adding calcium as CaCO3, vs. CaCl2 or Ca(NO3)2 has the further advantage
that you are also increasing the alkalinity (KH) and *buffering
capacity* -- the ability of the system to resist changes in pH.

If you have further questions, feel free to ask.

Best,

George


> 
> Date: Wed, 2 Jun 1999 17:29:51 -0400
> From: "Tom Brennan" <brennans at ix_netcom.com>
> Subject: Re: was APD V3#1063 & Calcium Deficiency
> 
> George wrote........
>  Mon, 31 May 1999 16:12:40 +0000
> From: George Slusarczuk <yurko at warwick_net>
> Subject: Re: Aquatic Plants Digest V3 #1063
> 
> Hello Ken,
> 
> Calcium chloride works well, but will acidify your water.
> 
> Marble chips (used in landscaping) in the filter will keep calcium
> carbonate at saturation level.
> 
> Dolomite (sometimes used as gardening lime) will also add magnesium to
> the water. Magnesium is needed for chlorophyll formation.
> 
> Best,
> George
> ============================================================
> 
> George/All....
> 
> What is saturation level?  Is this the point where Ca precipitates out of
> solution.  Also I have used "Sweet 'N Grow " Bakers Dolomite - Hy Magnesium,
> Pulverized Lime Stone
> 
> Chemical Analysis:
>                                                        Minimum Percent
> Calcium Carbonate (CaCO3)......................53.5%
> Calcium Oxide (CaO)...............................30.0%
> Magnesium Carbonate (MgCO3).................42.0%
> Magnesium Oxide (MgO)..........................20.0
> Elemental Magnesium (Mg)........................12.1%
> Elemental Calcium (Ca)............................21.4%
> Calcium Carbonate Equivalent (C.C.E.).....105.6%
> 
> and noticed it takes quite some time for the gH/kH to rise maybe days.  I
> thought by injecting Co2 it would devolve faster or almost immediately.  The
> Bakers Dolomite is a very fine powered and seems to dissolve upon slight
> mixing?  Is this what I want to use or should I seek out CaCO3 for kH/gH and
> use baking soda for increasing kH/gH.  By now you should have guess I am not
> a chemist!
> 
> Tom Brennan