Solubility of Hydrated Lime

[Bonebrake]

I wanted to post this to see if anyone else has experienced this...

I thought for a long time I was using saturated limewater only to find out I hadn't been.

The solubility of hydrated lime, Ca(OH)₂, Mrs. Wage's or some other brand, is 0.185 g / dL or 1.85 g / L or 6.993 g / gal. The solubility of dry lime, CaO, being less.

For a long time I had been using two heaping teaspoons per gallon assuming this was saturated. Only to find out no matter how much hydrated lime I piled on two teaspoons the most I could weigh out was 2.5 g per heaping teaspoon.

If you are using Mrs. Wage's or some other hydrated lime equivalent Ca(OH)₂ and do not have a decent scale to weigh out ~7 grams per gallon for saturation I would recommend using four level teaspoons or three heaping teaspoons to ensure you are achieving saturation if that is your goal.

Or you can measure the conductivity, but those meters are a little pricey.

 

[Randy Holmes-Farley]

The published bulk density of calcium hydroxide is about 0.64 g/mL, or 3.1 grams per level teaspoon. That would give 6.2 grams for 2 teaspoons, and more if they are heaping. So that is the general guideline.

http://www.powderandbulk.com/resources/bulk_density/material_bulk_density_chart_c.htm

It is certainly possible that Mrs Wages is fluffier than the norm. What device did you use to measure it?

FWIW, I use less than saturated limewater.

There is a lot more here:

What Your Grandmother Never Told You About Lime
http://reefkeeping.com/issues/2005-01/rhf/index.htm

 

[HighlandReefer]

I have always wondered if you should compress the pickling lime or not, when measuring out a teaspoon? I have not seen any references either way. :rollface:

 

[GAW]

Or you could just put in a couple of heaping spoonfulls, shake & let it settle, not worry about it and do just as good--- no sense in trying to turn something as simple as kalkwaser into rocket science.

 

[HighlandReefer]

How would you do this if your mixing vinegar with your kalk and not waste a lot of kalk?

 

[Bonebrake]

<a href=showthread.php?s=&postid=13437286#post13437286 target=_blank>Originally posted</a> by Randy Holmes-Farley
It is certainly possible that Mrs Wages is fluffier than the norm. What device did you use to measure it?

FWIW, I use less than saturated limewater.

What Your Grandmother Never Told You About Lime
http://reefkeeping.com/issues/2005-01/rhf/index.htm

Mrs. Wage's is extremely fluffy. I used a heaping measuring teaspoon that you would use in cooking and also a utensil teaspoon. Both were about ~2.5 g.

 

[bertoni]

Well, a pH meter can give you some idea of saturation. First, mix a tablespoon or so of lime into a cup of water, giving a saturated solution. Comparing the pH measurement of the meter on the two solutions would give a rough idea of the concentration. A conductivity meter would be easier to use, if it could measure the appropriate range.