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Re: PMDD/test kit/pond snails/A. gracilis

> Date: Mon, 12 Jan 1998 06:39:16 -0500 (EST)
> From: ac554 at freenet_carleton.ca (David Whittaker)
> I have a few questions which some of you might care to answer.
> The first concerns a batch of PMDD which I recently concocted.
> In 300 ml of distilled water were sequentially dissolved
> approximately
> 1.5 tsp micronutrient mix
> 1.5 tsp MgSO4:5H2O
> 1.5 tsp KNO3
> 2.0 tsp K2SO4
> 2.0 tsp CaCl2
> 0.5 ml muriatic acid
> Usually all goes well and the solutes dissolve properly.
> However, this time I changed the mix to include the calcium
> chloride as listed above. A white precipitate was formed which
> occupied 1/4 of the volume. A day in the refrigerator has
> subsequently increased the amount to about 3/4 of the volume
> of the jar. Would anyone care to explain the chemistry to me?
> What is the precipitate and will it dissolve on its own in
> the tank in less saturated circumstances?

My guess is calcium carbonate or calcium sulfate.  You could try 
boiling and cooling your water before use to drive off the CO2,
or mixing the CaCl2 in a separate solution if it turns out to be
the sulfate causing the precipitate.