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View Full Version : Identifying Calcite vs Gypsum



elixirmixer
02-01-2018, 09:46 PM
I am looking for help from anyone who can assist me in the knowledge required to test for gypsum in my calcite. Gypsum would actually be quite preferable in this instance I believe, and I'm sure there would be some gypsum in my calcite, however, I don't know how to tell the difference.

Calcite is simply calcium + carbon dioxide.
Gypsum is the same but with sulfur as well I believe.

Any thoughts from you chemists? Please?

EM.

JDP
02-01-2018, 10:16 PM
I am looking for help from anyone who can assist me in the knowledge required to test for gypsum in my calcite. Gypsum would actually be quite preferable in this instance I believe, and I'm sure there would be some gypsum in my calcite, however, I don't know how to tell the difference.

Calcite is simply calcium + carbon dioxide.
Gypsum is the same but with sulfur as well I believe.

Any thoughts from you chemists? Please?

EM.

Calcite = calcium carbonate. Gypsum = calcium sulfate. It's not "rocket science", really.

As for how to know if there is some gypsum mixed in with your calcite: dissolve a sample of it in diluted acetic acid. Does it leave a white insoluble substance? Yes? Then it might be some gypsum mixed with the calcite (but then again it could also be other things that do not dissolve in that acid, like silica, for example. But the simple test will give you an idea if your calcite has many or few impurities that do not dissolve in diluted acetic acid.)

elixirmixer
02-01-2018, 10:50 PM
Nice, got any maths on the acetic acid for say... 100g of calcite? Pretty please? Since my 'incident' I haven't been able to do uni level maths anymore.

JDP
02-02-2018, 12:41 AM
Nice, got any maths on the acetic acid for say... 100g of calcite? Pretty please? Since my 'incident' I haven't been able to do uni level maths anymore.

Just keep adding portions of the dilute acid to the powdered or coarsely crushed calcite sample until it "fizzles" no longer and you don't see any more foam/bubbles forming. That means that pretty much all the carbonates have been decomposed and soluble acetates have formed.

elixirmixer
02-02-2018, 01:17 AM
JDP, if I could bother you again, could you please explain to me the different between treating calcite with acetic acid, and treating it in acetone? :D:D:D:o

JDP
02-02-2018, 01:36 AM
JDP, if I could bother you again, could you please explain to me the different between treating calcite with acetic acid, and treating it in acetone? :D:D:D:o

https://i.imgur.com/tZuKjh5.jpg?2

elixirmixer
02-02-2018, 02:10 AM
If treating calcite with acetic acid makes calcium acetate, then treating calcite and/or calcium with acetone makes what??

Dragon's Tail
02-02-2018, 03:24 AM
If treating calcite with acetic acid makes calcium acetate, then treating calcite and/or calcium with acetone makes what??

a mess :D

edit: Sorry I couldn't resist. And I figured I'd better look into this before I cat myself into trouble. I can't find solubility information for either with acetone, so my guess would be nothing at all happens.

edit 2: gypsum is a drying agent for acetone, aparently, but doesn't dissolve. CaCO3 is listed by pubchem as insoluble in acetone.

elixirmixer
02-02-2018, 06:33 AM
The reason I ask, is because calcium acetate is one of these beautiful chemical obscurities where the dissolution rate decreases with temperature. This is an important property when identifying substances which will "solve et coagula" at low temperatures, and more importantly, repetitively.

Florius Frammel
02-02-2018, 08:20 AM
It is not really an obscurity.
When a salt is solving in a solvent the ion lattice is destroyed and the particles of the solvent surround the ions.
The destroying needs energy (endothermic) and the surrounding sets energy free (exothermic).
If the amount of energy needed is higher than the amount of energy set free the process needs additional energy from outside (the warmth of room temperature). If you solute for example NH4NO3 in water and stir with a thermometer you will obeserve a cooling, for the process takes additional energy from outside. If you do the same experiment with NaOH it is the other way round and a heating is obeserved.

Usually exothermic reaction and solution processes are prefered by nature as there is always the lowest possible salary of energy is wanted by the process.
The reason why endothermic reactions or solution processes take place anyways is because the state of chaos is preffered by nature too. Look at a building that's a hundred years old. It will consequently fall apart voluntary. Same with ion lattices in a solution.

If the entropy (chaos) is higher than the enthalpy (energy) those processes can take place, even if it is an endothermic process.

Now you can influence this processes by means of temperature. Endothermic processes need energy and therefore prefer higher temperatures. Exothermic reactions produce energy and therefore prefer lower temperatures. It's always a kind of chemical equilibrium between the material you start with and the material you end with. By means of energy you can shift the equilibrium to your wanted result.

JDP
02-02-2018, 02:35 PM
The reason I ask, is because calcium acetate is one of these beautiful chemical obscurities where the dissolution rate decreases with temperature. This is an important property when identifying substances which will "solve et coagula" at low temperatures, and more importantly, repetitively.

This is NOT the "solve et coagula" the alchemists had in mind, though. The water of solution DOES NOT PERMANENTLY JOIN WITH THE DISSOLVED MATTER. Common water will NEVER make such a union, it can always be separated from whatever it dissolves. What you need is the "water" (i.e. the secret solvent) of alchemy.

elixirmixer
02-02-2018, 08:00 PM
This is NOT the "solve et coagula" the alchemists had in mind, though. The water of solution DOES NOT PERMANENTLY JOIN WITH THE DISSOLVED MATTER. Common water will NEVER make such a union, it can always be separated from whatever it dissolves. What you need is the "water" (i.e. the secret solvent) of alchemy.

I agree

Schmuldvich
02-02-2018, 08:32 PM
I agree

What did you say?

I can't hear you!!!

Maybe if you UNDERLINED YOUR WORDS and use ALL CAPITALS and sometimes "quotation marks" or even blue text instead of black text we would understand what you are actually trying to convey in EVERY POST that you decide to post on this message board from here on out.

Until then, we WILL NOT be able to hear you!

EVER!

;)




Did you ever get a chance to take pictures of your cave journey?

I would love to see some of the minerals you're working with!

JDP
02-02-2018, 10:15 PM
What did you say?

I can't hear you!!!

Maybe if you UNDERLINED YOUR WORDS and use ALL CAPITALS and sometimes "quotation marks" or even blue text instead of black text we would understand what you are actually trying to convey in EVERY POST that you decide to post on this message board from here on out.

Until then, we WILL NOT be able to hear you!

EVER!

;)

It's done to EMPHASIZE VERY IMPORTANT POINTS, SPECIALLY FOR THOSE WHO MIGHT NOT HAVE GOTTEN THEM YET, OR FOR PARTICULARLY STUBBORN PEOPLE WHO REPEATEDLY KEEP FALLING FOR THE SAME MISTAKES, but I don't think I need to tell YOU that ;)

The color text is done in order to MORE EASILY DISTINGUISH a quoted source from the default black text for this forum's posts (like the one you are reading right now), but I see by your above sarcastic "comment" THAT YOU HAVE FAILED TO NOTICE THIS TOO and are still puzzled by it. :)

elixirmixer
02-02-2018, 10:59 PM
Haha, you guys are funny. The rocks arnt going anywhere smernoff, when my internet issues are resolved (probably about this time next year at the rate they are going) then I'll have lots of pictures for you.

The cave journey has been great!! Now I'm back to house Reno's cause I don't want to die in a hole.

If you send me your email I can email some photos for you if you like, something about the AF uploaded doesn't work with my phone because I can't click and drag the pictures into the Dropbox.

Kibric
02-03-2018, 12:02 AM
you guys would be great friends if you met
you both really care about what the truth is
for an internet forum its pretty tame ribbing :D