COA Analysis of Bulk White Hydrated Lime (Calcium Hydroxide/ Kalkwasser)

M

Mohammed

New member
Hi all,

I've been recently trying to source kalk in bulk and managed to find a supplier who advises that there are only 2 mines in our country and that they own both and package for most pharmacies etc.

I'm led to believe that kalk has self purifies capabilities hence the sediment we normally just clean out occasionally. Please can someone look at the COA and advise if its suitable to use. Is the Sulphur and Copper levels something I should be concerned about. Is this possibly where those elevated levels in those triton test results come from as a lot of reefers use kalk.

The company just sent me the COA. Here is it below:


Typical Analysis of Premier White Hydrated Lime:


Ca (OH)2 : > 92%
Available Lime as CaO : Typical 70% (ASTM) (min 65%)

Ca CO3 : < 5%
SiO2 : < 1.5%
Sulphur (S) : < 0.03%
Mg, as MgO : < 1.8%
Iron (Fe) : < 0.08%
Aluminium (Al2O3) : < 0.4%
Manganese (Mn) : < 40 ppm
Cobalt (Co) : < 50 ppm
Zinc (Zn) : < 50 ppm
Nickel (Ni) : < 50 ppm
Copper (Cu) : < 15 ppm
Chromium (Cr) : < 50 ppm

Particle size : < 5% retained on 106 µm
Free Moisture : < 1%

Thanks
 
Yes, that will be fine to use. Calcium hydroxide isn't mined directly. Instead, calcium carbonate (limestone) is mined and the calcium oxide/hydroxide is formed from heating in a kiln, which drives off CO2 to form Calcium oxide/hydroxide.

When this is dissolved in water, the pH of the solution levels out at about 12.5. At this pH, most metals are not soluble, and precipitate as the metal hydroxide and/or carbonate. So the clear solution will contain little to no metal contaminants.
 
Most of us use food grade calcium carbonate with the following impurities:

Table 1. Typical Chemical Analysis of Food Grade Calcium Oxide


Impurity

Concentration in Solid CaO from Manufacturer

Approximate Calculated Concentration in Saturated Limewater


Si 0.35% 4 ppm
CaO 98.0% ---
Magnesium & Alkali Salts 1.0% 11 ppm
Fluoride 75 ppm 80 ppb
Lead <0.5 ppm <5 ppb
Arsenic <1.0 ppm <1 ppb
Acid Insoluble Substances 0.20% ---
Heavy Metals 2 ppm 2.2 ppb
Al 0.10% 1 ppm
Fe 0.04% 0.4 ppm
S 0.01% 0.1 ppm
CO2 0.40% 4 ppm
P 50 ppm 55 ppb
Mn 12 ppm 13 ppb
Ca 69.97% ---
Crystalline Silica <0.1 % < 1 ppm


While the high pH of fully saturated limewater does precipitate some impruites provided the precipitants from the slurry at the bottom are not dosed; it may not handle all of it at some of the levels noted in the product you are considering;it might be ok but I'm a warry of it. This article has more:

http://www.advancedaquarist.com/2003/5/chemistry
 
The impurity levels. It's 65% vs 98% over all for lime content. The metals are much higher.
 
Ok. That throws a spanner in the works.

Not trying to beat it, just trying to source larger quantities as the pharmacies only sell 50g packs and no CoA anywhere on the packaging.
 
Ok found another supplier of Calcuim Hydroxide Lab Grade.

Heres the CoA. Does this look better at 98.5% Sorry had to type the CoA out so first is Parameter followed by Limits and then the Result of the CoA.

Parameters Limits Results

Description Powder Powder
Colour White White
Identification Conforms Conforms
Carbonate (CO3) Conforms Conforms
Flouride (F) Max 0.005% <0.005%
Acid-insoluble substances Max 0.5% <0.5%
Arsenic(As) Max 0.0003% <0.0003%
Lead (Pb) Max 0.0002% <0.0002%
Magnesium and Alkali Salts Max 4.8% <4.8%
Assay Ca(OH)2 95.0-100.5% 98.5%
 
Yeah, that would work. BTW, realize that the previous C of A that you posted didn't indicate that the material was highly contaminated with stuff you don't want (such as heavy metals). The "Available Lime as CaO: typical 70%" means that when the Ca(OH)2 is converted to CaO, 70% of the powder is CaO.

Because of the difference in molecular weight between Calcium hydoxide and Calcium oxide, then 1 kg of powder that is 92% Calcium hydroxide will have 700 g of Calcium Oxide in it if it's dehydrated by heating. The vast majority of the remainder is Calcium Carbonate, which is the starting material for making Calcium Oxide/Hydroxide. Calcium carbonate is insoluble, so you won't be "getting it all" when you dissolve the material in water.

But because of the way that we use calcium hydroxide/calcium oxide, which is to prepare a saturated solution, we don't "get it all" anyway.
 
Ok perfect, going with the second supplier then, also the second suppliers Calcium Hydroxide is imported from Germany so it must be good. Lol.
 
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