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Brown water!
OK, I went back and did a search. This message was from Rod Farlee
who IS a chemist. this is what he said on 6/16/1999 Ingrid "But this "pH pill" is not the "one size fits all", "toss it in and forget it" remedy that the ******** suggests it is. It certainly works, but with some caveats. It raises GH (general hardness, calcium) more than calcium carbonate (limestone) alone does. That's because it contains calcium sulfate (gypsum), which is much more soluble than calcium carbonate, and which raises GH but not KH (alkalinity, bicarbonate). So unless one has very soft, slightly alkaline water to begin with, care should be taken. GH and KH should both be monitored. If GH is getting too high, take it out, and add baking soda if needed to raise KH. Or limit the amount to less than 1 lb/1000 gallons, to ensure GH does not continue to rise. If much larger amounts of plaster of Paris are added, it just won't work. Gypsum is 170 times more soluble than calcite. Gypsum will continue to dissolve, and push GH "off the scale". Through the common ion effect (calcium), this will suppress dissolution of the calcite (calcium carbonate), so KH will remain low. If a very large amount were used, GH and pH would go up, and KH would actually go down, and the pond might get cloudy with calcite precipitation. That would be a Bad Thing: it's the next step on the road to an alkali lake. Gotta watch for that. Happily, it takes some weeks for the "pH pill" to dissolve anyway, so these gradual changes can be monitored. And the effects of an "overdose" are ameliorated if one's water contains a substantial magnesium component in it's GH (the average eastern or midwestern river does, Ca/Mg ~ 4). (Reasons: MgCO3 is much more soluble than CaCO3, and it interferes with calcite cystallization so allows supersaturation to occur. This reduces high GH driving KH down.) Finally, if one receives regular rainfall, one might never see these overdose effects. But the potential is there, and I treaded close to it before I understood what was happening." |
#2
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Brown water!
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#3
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Brown water!
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