Kalk chemistry

[Jon_Hewett_85]

I was wondering as to how long before a bucket of kalk can sit uncovered before it looses it's usefulness and the Calcium hydroxide reacts w/ the co2 in the air until you have a Calcium Chloride solution. I usually add it to the topoff resevoir (which is covered) As soon once it has settled...usually 6-8 hours. I was wondering how long it's good for.

[logical]

Hi, I'm new to using Kalk, and mix it in a 5 gallon water jug for topoff. Are you saying I need to wait until the Kalk settles before adding it to sump? So far I have just mixed it up and immediately added to sump. I thought the "cloudy" look was the good stuff?

Thanks, Bryan

[Randy Holmes-Farley]

Some people dose milky limewater and seem to have fine tanks. Or at least they did dose it before switching to CaCO3/CO2 reactors.

Personally, I do not like to see milky limewater dosed into tanks for two main reasons:

1. More impurities in the lime get into the tank. If you let it settle, many heavy metal oxides and hydroxides will precipitate and not get to the tank.

2. The milky lime will contain either undissolved calcium hydroxide, calcium carbonate, or both. I don't like to see either get into the tank as the solids can cause a precipitation event (CaCO3 precipitation) or otherwise reduce the calcium and alkalinity levels.

[Randy Holmes-Farley]

The length of time that limewater lasts depends on a variety of factors.

I use a 44 gallon trash can with a loose lid over a few week period without problem.

I've measured the decline in limewater potency over time as it sits open in a 1 gallon container (via conductivity). If there are excess solids on the bottom, then it stays close to saturation for a long time (days anyway). In that case, calcium hydroxide is dissolving about as fast as calcium carbonate is precipitating. in some cases, the liquid never clears, but sets of a situation where CaCO3 is slowly forming throughout the fluid.

If there is no excess solid material, then it will begin to decline substantially after a day or so, but how fast depends on mixing, whether you break the surface crust, etc.

[Jon_Hewett_85]

If left to long would it be posible for said heavy metal oxides and so forth to dissolve back into the solution?

[Randy Holmes-Farley]

No, I don't think that is likely before the material mostly became calcium carbonate (i.e., useless).