Kalkwasser analysis

[Harpo]

Randy:

I hear frequently about possible heavy metal contamination of kalkwasser. Has any analysis of various sources been done to see if true and if true how bad?

I live in an area that is hot and low humidity in summer and cool with very high humidity in winter. My open top 135 will evaporate over 3 gal/day in summer and less than 1/2 gal this time of the year. I've found my calcium levels stay much more stable by direct addition of kalkwasser to the tank rather than top off water but I'm concerned about long term heavy metal accumulation.

I've been using Kent kalkwasser but would I have less contaminants if I went to reagent grade calcium hydroxide? Cost would be approximately 2x.

Thank you, Mark

[Randy Holmes-Farley]

There is metal contamination in all of them, but how much will depend on what type of material. I've not seen any detailed heavy metal analysis of any of them, but the manufacturer that I use shows some:

http://www.mississippilime.com/products/product.asp?dept%5Fid=209&pf%5Fid=20941&tabsetting=2

TYPICAL CHEMICAL ANALYSIS
Si 0.35%
CaO 98.0%
LOI 0.50%
Magnesium & Alkali Salts 1.0%
Fluoride 75 ppm
Lead <0.5 ppm
Arsenic <1.0 ppm
Acid Insoluble Substances 0.20%
Heavy Metals 2 ppm
Al 0.10%
Fe 0.04%
S 0.01%
CO2 0.40%
P 50 ppm
Mn 12 ppm
Ca 69.97%
Crystalline Silica <0.1

Whether higher grades have less impurities, I'm not sure. If you have a place that sells high quality grades, you might ask for a technical sheet on its purity.


That said, I don't believe that most of these metals will make it to the tank if you use settled limewater because many of them are insoluble at the high pH (e.g., copper). This is a bonus for limewater users that is not available to any other calcium and alkalinity supplementation scheme.

Here's are two threads where we discuss those issues:
http://archive.reefcentral.com/forums/showthread.php?s=&threadid=140108

http://archive.reefcentral.com/forums/showthread.php?s=&threadid=115200

I've found my calcium levels stay much more stable by direct addition of kalkwasser to the tank rather than top off water but I'm concerned about long term heavy metal accumulation.


What do you mean by direct addition? Solids to the tank? That will deliver all of the impurities into the water, and negates your bonus.:D

[Harpo]

Yes. You've discovered my shameful secret. I'm one of the lazy bums that uses Anthony Calfo's method of adding kalk slurry directly to tank or sump.

Therefore you can appreciate my interest in actual heavy metal content in various grades of calcium hydroxide and whether I can cut the heavy metal content by stepping up to reagent grade.

Mark

[Randy Holmes-Farley]

Therefore you can appreciate my interest in actual heavy metal content in various grades of calcium hydroxide and whether I can cut the heavy metal content by stepping up to reagent grade.

I don't know what the heavy metals limits are to reagent grade calcium hydroxide or oxide (maybe someone else has it handy).

Many brands give a lot analysis on the label, but it will, at best, lump all heavy metals together, and not list them individually. In that case, iron shows up like lead and copper, so it is hard to say how much toxic heavy metal might be present.

Here's a page that shows the food grade (FCC/USP) specification limits:

http://www.mississippilime.com/products/product.asp?dept%5Fid=310&pf%5Fid=31004&tabsetting=2

In that case, heavy metals are less than 30 ppm, while the actual typical material that these folks sell is 1.33 ppm. So the moral of the story is that actual metals may be far below whatever the standards say the max should be.

[Harpo]

Thank you, Mark

[Habib]

I don't know what the heavy metals limits are to reagent grade calcium hydroxide or oxide (maybe someone else has it handy).

Depending on the source it is 30 - 50 ppm.

There are however many other grades which are perhaps better (and cheaper).

[Harpo]

Habib:
What would be the perhaps better and cheaper grades?

Thank you, Mark

[Habib]

Mark,

What would be the perhaps better and cheaper grades?

I have not looked in detail at the links Randy has given but there are some food grades which are much better than reagent grade.
Some of them are more expensive than reagent grade but some are cheaper.

So IMO it is wise to get a as detailed composition and pricing.
Then it is a matter of comparing.

So sorry that I can not direct you to a source in the USA but perhaps Randy's source (I have not folowed the complete threads) is good enough.

HTH

[Harpo]

Habib:

Thank you, Mark