Sciencemadness Discussion Board - Dolomite chalk

Dolomite chalk

Fantasma4500 - 2-2-2014 at 07:45

huge bags for small prices are always interesting, as a chemist i see use in everything.. however...
something i paid abit more attention to --- magnesium
i found some data on what this 'dolomite chalk' contains

DOLOMIT KALK
12% Mg
51% CaCO3
40% MgCO3

as it talks about MgCO3, i suppose Mg isnt the MgCO3?? would this really mean theres magnesium METAL in some sort of mesh or large chunks within it??

as i tried to figure out how to seperate this stuff out i got to H2SO4 as being useful to some extent..

H2SO4 + CaCO3 + MgCO3 > H2O + MgSO4 (aq) + CaSO4 (s) + CO2
~~not balanced, just showing the idea~~

but.. H2SO4 and magnesium metal would be quite a waste.. i really cant come up with an idea to seperate out the magnesium metal from the others.. heating the whole bunch wouldnt give much magnesium im sure, it would simply be stuck in the carbonates
any ideas?

25kg ~3.3 euro --- 3kg Mg, in case it has 12% magnesium metal per weight

bfesser - 2-2-2014 at 08:23

Quote: Originally posted by Antiswat

as it talks about MgCO3, i suppose Mg isnt the MgCO3?? would this really mean theres magnesium METAL in some sort of mesh or large chunks within it??

No, there is no free metallic magnesium.

[Edited on 2.2.14 by bfesser]

Morgan - 2-2-2014 at 08:28

Maybe it's the amount available to plants if it's a fertilizer.

[Edited on 2-2-2014 by Morgan]

Sedit - 2-2-2014 at 09:01

Its showing 103% that should be a red flag for you right there.

Morgan - 2-2-2014 at 12:58

Here's a 25 kg bag of 55/30.
http://www.ebay.de/itm/25kg-Dolomitkalk-Dolomit-Rasenkalk-Ga...

Agricultural tidbits perhaps an explanation.
"The quality of agricultural limestone is determined by the chemical makeup of the limestone and how finely the stone is ground. To aid the farmer in determining the relative value of competing agricultural liming materials, the agricultural extension services of several universities use two rating systems.[10] Calcium Carbonate Equivalent (CCE) and the Effective Calcium Carbonate Equivalent (ECCE) give a numeric value to the effectiveness of different liming materials.
The CCE compares the chemistry of a particular quarry's stone with the neutralizing power of pure calcium carbonate. Because each molecule of magnesium carbonate is lighter than calcium carbonate, limestones containing magnesium carbonate (dolomite) can have a CCE greater than 100 percent.[11]"
http://en.wikipedia.org/wiki/Agricultural_lime#cite_note-11

WHAT IS CALCIUM CARBONATE EQUIVALENT?
http://hubcap.clemson.edu/~blpprt/bobweb/BOBWEB2.HTM

Zyklon-A - 2-2-2014 at 13:04

Using it to make MgSO₄/CaSO₄ would be a waist of sulfuric acid, because CaSO₄ is very cheap as is its Mg counter-part.

Fantasma4500 - 3-2-2014 at 05:52

Typisk analyse:
Calciumcarbonat (CaCO3) 51,0%
Magnesiumcarbonat (MgCO3) 40,0%
Magnesium (Mg) 12,0%

http://www.horticoop.dk/datablade/goedning/azelis-broeste/Do...
'typical analysis'
how it is not 100% is a really good question

about MgSO4, only thing ive seen coming close to it was 'special salt'
as i found the datasheet for this 'special-salt' i realised the special thing about it is that it contains --- Sodium Chloride
i dont even think you can buy magnesium sulfate in my country, i would say using magnesium metal to make magnesium sulfate would be a massive waste

magnesium and calcium would still be possible to extract from this, gypsum is in the matter of fact decently pricey where im at, i recall around .. 10 euro for a kg..?
sulfuric acid you can buy online very cheap if you manage to find one of those suppliers that sells pool chemicals by the kg and not by volume, 50% 'tower acid' is what concentration i recall they sell really cheap

anyhow, bfesser.. how can you be entirely sure it doesnt contain free metallic magnesium? because it says magnesium twice, it shows a chemical formula where both magnesium, calcium and carbonate is as one, and even 103% by weight

TheChemiKid - 3-2-2014 at 06:50

Quote: Originally posted by Antiswat

DOLOMIT KALK
12% Mg
51% CaCO3
40% MgCO3

That adds up to 103%, please correct that.

Pyro - 4-2-2014 at 12:59

I believe it is because Mg and MgCO3 ''overlap''
if Mg is the total amount of magnesium
so you could have 40% MgCO3, and X% MgXX that, combined with CaCO3, contain 12% Mg

Does anybody understand this? I'm having trouble painting the picture.

EDIT: if you isolated Mg metal from the chalk mix in a 100% yield you would have 12g Mg for every 100g of dolomite chalk.
(because there might be MgSO4, Mg(NO3)2, Mg3(PO4)2,... in it as well as MgCO3)
better?

[Edited on 4-2-2014 by Pyro]

Lost In Translation / Mystery Solved

bfesser - 4-2-2014 at 14:57

<a href="https://en.wikipedia.org/wiki/Dolomite" target="_blank">Dolomite</a> <img src="../scipics/_wiki.png" /> CaMg(CO3

2 is 13.181% Mg by mass. <a href="https://en.wikipedia.org/wiki/Dolostone" target="_blanK">Dolostone</a> <img src="../scipics/_wiki.png" />, a common rock composed of primarily dolomite, would be slightly less than 13.181 % Mg by mass. Assuming that the contents are powdered dolostone with a purity of 91% dolomite1, the product would contain 12 % Mg by mass. Your <a href="https://en.wikipedia.org/wiki/Agricultural_lime" target="_blank">agricultural lime</a> <img src="../scipics/_wiki.png" /> ('dolomit kalk') is—<a href="https://en.wikipedia.org/wiki/Occam's_razor" target="_blank">beyond a reasonable doubt</a> <img src="../scipics/_wiki.png" />—powdered dolostone in a bag. The remaining 9 % is likely quartz grains and other minerals commonly present in sedimentary rock, and possibly a little water of hydration.

24.3050 g/mol Mg &div; 184.401 g/mol CaMg(CO3

2 × 100 % ≈ 13.181 % Mg by mass

40 % MgCO3 + 51 % CaCO3 = 91 % MgCa(CO3

2

91 % CaMg(CO3

2 × 13.181 % Mg = 11.99471 % Mg –(2 s.f.)→ 12 % Mg by mass

Quote: Originally posted by Antiswat

huge bags for small prices are always interesting … 25kg ~3.3 euro

Nothing turns a profit quite as easily as open-pit mining a ubiquitous rock, grinding it to a powder, and stuffing it into a bag with a fancy label.

1Of course, it's not necessarily 91 % dolomite, but 'available' magnesium, calcium, and carbonate in different minerals including dolomite that neatly add up to 91 % [CaMg(CO3

2] during the crude analysis. The actual minerals that are attributed to the percent dolomite would include dolomite, calcite (CaCO3

, magnesite (MgCO3

, ankerite (Ca(Fe,Mg,Mn)(CO3

2

, etc.

P.S. Dolomit Kalk, taken to be German/Danish, translates to dolomite lime in English. Chalk (CaSO4

is Kreide in German (<a href="http://books.google.com/books?id=0WRIAAAAMAAJ" target="_blank">ref.</a> <img src="../scipics/_ext.png" />

and Kridt in Danish.

[Edited on 5.2.14 by bfesser]

testimento - 4-2-2014 at 18:34

Some substances may come cheap, but the process of purification may become a really expensive or tedious job.

Fantasma4500 - 5-2-2014 at 08:29

http://www.ebay.de/itm/2-x-28-Kg-pH-Senker-Minus-Fluessig-Ve...

might come cheap, but imagine the amounts of MgSO4 you would get from it, the amounts might be slightly impure, but we all gotta have some goal with our everyday lives
its alot of H2SO4, its legit ''bulk'' and with the prices in my country for stuff thats seen as average chemicals equal to table salt.. whew.. its near that it would be cheaper to buy 10L H2SO4 and 25kg dolomite LIME rather than trying to spend a second to find magnesium sulfate within borders

but as bfesser says, it may sound cheap to us, but it was even cheaper to mine, and even cheaper to mine, powder and label, otherwise they wouldnt sell it, they still manage to drag profit from it

the reason i didnt perfectly translate it was because i just copypasted the section from the datasheet showing what it contains, my bad not translating it into lime but rather chalk

i still dont know how there can be more than there is, assuming % is by weight, that would mean theres 750g extra (3%) ?? if 25kg is 100%

bfesser - 5-2-2014 at 09:24

Antiswat, MgSO4 as <a href="https://en.wikipedia.org/wiki/Magnesium_sulfate#Medical" target="_blank">epsom salt</a> <img src="../scipics/_wiki.png" /> is likely easy to find and cheap, even in Denmark. Your local pharmacy should carry it in packages resembling American milk cartons or sometimes plastic bags. Epsom salt generally refers to the heptahydrate, but the last sample I analyzed was 37.9 % H2O by mass, which (assuming homogeneity) indicated the tetrahydrate, MgSO4 · 4 H2O.

As for the "typical analysis," I thought I demonstrated it quite clearly, but evidently not clearly enough. Allow me to elaborate:

On many such products, especially agricultural fertilizers, the percents are given as parts out of the whole. When they list 12 % Mg, they mean that 12% of the total mass of the contents of the bag was determined to be magnesium. Likewise, 40 % of the total mass is presumed MgCO3 and 51 % of the total mass CaCO3. Because each identified component is measured in percent mass of the whole, the percentages are not additive. It's a bit different from a standard elemental analysis.

25 kg dolomit kalk × 12 % Mg (by mass) = 3 kg Mg (by mass)

25 kg dolomit kalk × 40 % MgCO3 (by mass) = 10 kg MgCO3 (by mass)

25 kg dolomit kalk × 51 % CaCO3 (by mass) = 12.75 –(2 s.f.)→ 13 kg CaCO3 (by mass)

25 kg dolomit kalk × 9 % impurities = 2.3 kg waste (likely insoluble in H2SO4

So, a 25 kg bag of dolomit kalk would contain approximately 3 kg magnesium (bound up in dolomite and other minerals), ca. 10 kg of material that acts like magnesium carbonate (the 3 kg Mg is part of this

, and ca. 13 kg of material that acts like calcium carbonate during the crude chemical analysis and use as a fertilizer. I can't think of a clearer way of explaining this; so if you're still having difficulty, perhaps someone else would be kind enough to provide a simpler perspective.

If you're hoping to extract the magnesium from dolomit kalk as magnesium sulfate, keep in mind that the separation will be time consuming and tedious. The source dolostone would undoubtedly contain a small proportion of clay minerals in that other 9 %, which are a real pain in the ass to filter. Prolonged settling (hours–days) followed by careful decanting through a large filter would be necessary. Also, quartz grains (another part of that 9 %) will easily scratch borosilicate glassware, and inflict permanent surface damage to porcelain mortars & pestles—I know this from experience. Below are photos of samples of both dolomit kalk and epsom salt, respectively. I know which I'd rather purify...

[edit] A few related calcualtions:

CaMg(CO3

2 + 2 H2SO4(aq) → CaSO4(aq) + MgSO4(aq) + 2 H2O + 2 CO2(g)

44.0095 g/mol CO2 &div; 60.01 g/mol CO32- × 100 % ≈ 73.5 % of CO32-(aq), by mass, liberated as CO2(g)

60.01 g/mol CO32- × 2 mol CO32- / mol CaMg(CO3

2 &div; 184.401 g/mol CaMg(CO3

2 × 100 % = CaMg(CO3

2 is 65.09 % CO32-, by mass

25 kg dolomit kalk × 91 % CaMg(CO3

2 × 65.09 % CO32- × 73.5 % CO2(g) ≈ 11 kg CO2(g) / bag (assuming no other carbonates present!

And if you were to take into account the third oxygen of the carbonate which reacts to form water, you're wasting a hell of a lot of your initial 25 kg. I'd appreciate it if someone double-checked all of my calculations—I must have made at least one error.

[Edited on 7.2.14 by bfesser]

ScienceSquirrel - 6-2-2014 at 16:33

I suspect that the extraction of magnesium sulphate from dolomite is easier than bfesser suggests given a cheap source of sulphuric acid.
As a starting point I would add dolomite powder slowly to a 10% excess of 50% suphuric acid.
After it has ceased to effervesce, bring it to the boil and swirl. The calcium sulphate and clays should stick together.
Pour the solution through a sand bed filter and then concentrate and crystallise.
Alum, etc were made by similar methods historically so it should work.
But it is a tough approach to Epsom salts.
If you cannot buy Epsom salts, have a look at magnesium carbonate. Cheap as chips and used as gymnastic chalk, etc. Dissolve in sulphuric acid, which you have, and crystallise.

Fantasma4500 - 8-2-2014 at 03:48

not a single problem, my mind passed that thought on, i had it but i didnt keep it.. i see now.. impurities is the last 9% (:

i get your idea, its cleaner and less messy, but its not as bulky, turning something not quite useful into a decently useful pure chemical is my quest!

i got a 45L glass vial, and i would just stir it once then let it settle, i would need to add small amounts of acid at a time, simply because of the fact that CO2 is by some considered toxic
it would be more correct to say you cannot live on CO2, its quite alot CO2 infact, i recall having some specific use for CO2.. ohwell..

on a sidenote i googled epsom salt, i only went to one store which has all sorts of healthy stuff -- including laxatives such as erythritol, they didnt have any, and of all stores they should have it, ive never actually seen it in stores and its actually only those secondary health stores, those private owned ones you know, not to mention they charge absolutely full price

its not that much having the product, its the process, a cheap process that can give abit experience handling bulk amounts of chemicals

anyhow, sciencesquirrel -- i think that an excess of H2SO4 would be problematic, taking into consideration that CaMg(CO3)2 is insoluble then its simple to decant off.. H2SO4 is a hell because it makes holes in clothes, and even in yourself if you have it concentrated enough
also, magnesium carbonate?? i thought they used MgO for that stuff??
but letting the whole lot settle is not something thats gonna take alot of effort, just leave it alone and come back later on, scoop it up and let it evaporate in a large surface glass pan