Sciencemadness Discussion Board - Calcium Nitrate from Magnesium Nitrate

Calcium Nitrate from Magnesium Nitrate

Chemistry Alchemist - 25-7-2012 at 01:48

Hello fellow smart people its me again

Magnesium nitrate is a fairly common chemical i can get my hands on for a cheap price for about 500grams, Calcium nitrate on the other hand is pretty hard to get and it could be a very fun and useful chemical for pyrotechnics or just a good nitrate, its hard to get my hands on becuase i dont have nitric acid so i cant simply add calcium carbonate to nitric acid to get Calcium Nitrate, so i have been thinking how can i make it out of Magnesium Nitrate. Magnesium Hydroxide and Carbonate are both insoluble so if i could get something like Calcium Carbonate or hydroxide and mix it with Magnesium nitrate maybe it will precipitate Magnesium OH or CO3, but then i relised wont work due to both the Ca(OH)2 and CaCO3 are insoluble so it wont work... So it got me thinking even more... what is a soluble calcium salt which i can precipitate the magnesium and get calcium nitrate. Then it hit me... Calcium Bicarbonate, It is soluble in water 16grams at 0 Deg C or 18 grams at 100 Deg C. This is where a question needs to be answered. Does this reaction work.

CaCO3 + CO2 + H2O --> Ca(HCO3

2

If this reaction does work then would it be possible to make a solution of Magnesium nitrate and have the freshly prepared Calcium bicarbonate in excess and mix the 2 together as the following reaction.

Mg(NO3

2 + Ca(HCO3

2 --> MgCO3 + Ca(NO3

2 + CO2 + H2O

Does all this seem to be right?

weiming1998 - 25-7-2012 at 03:31

Quote: Originally posted by Chemistry Alchemist

Hello fellow smart people its me again

2 + Ca(HCO3

2 --> MgCO3 + Ca(NO3

2 + CO2 + H2O

Does all this seem to be right?

Unlike the alkali metal bicarbonates, alkali earth bicarbonates (or indeed any metallic bicarbonates apart from the alkali metals) is extremely unstable due to the bicarbonate ion decomposing to carbonate, H2O and CO2 in the presence of even a mildly acidic cation, because of how weak an acid H2CO3 is. The reaction of CO2 and H2O to form Ca(HCO3)2 indeed works (as demonstrated by bubbling excess CO2 through lime water, the precipitate disappears), but calcium bicarbonate is very unstable. It will decompose readily, especially in high concentrations (calcium bicarbonate exists in very dilute solutions in "hard" water and other water sources) and cannot be isolated. Magnesium bicarbonate is slightly more unstable than calcium bicarbonate (you can predict this by the increased acidity of the Mg2+ ion) but can still possibly exist in solution (sorry, can't provide references, because all the search result relates to some bicarbonate drink). It would be difficult to create an adequately concentrated solution of Ca(HCO3)2 to perform the double displacement reaction with magnesium nitrate that you suggested, and possible complications could occur with soluble magnesium bicarbonate and magnesium carbonate hydrate as well. So, this idea is not good practically.

It is difficult to pick an insoluble magnesium salt that has the same anions as a soluble calcium salt, so I don't think double displacements are the way to go. Try making nitric acid with the magnesium nitrate, then react with Ca(OH)2/CaCO3.

AJKOER - 25-7-2012 at 05:16

Fine comments and feedback by Weiming1998.

However, before you completely bury your CaCO3 idea, to be complete, you may consider mixing on a small scale a fresh precipitate of Calcium carbonate with hot aqueous magnesium nitrate.

My reasoning is I believe I have read about at least one reaction that uses a fresh precipitate of Calcium carbonate to effect a reaction that would otherwise not proceed. Most likely still won't work, but may be worth the effort as you do have a half a kilo of the stuff.

Chemistry Alchemist - 25-7-2012 at 07:09

i know that calcium bicarbonate is unstable and can easly convert back to carbonate, so i was saying making a new batch of bicarbonate and then straight away filter it directly into magnesium nitrate

bbartlog - 25-7-2012 at 07:59

I believe magnesium salts tend to be more soluble than their calcium counterparts, so it is unlikely that you can find a way to selectively precipitate the magnesium while leaving the calcium in solution. I think your best bet if you have the equipment is to add H2SO4 (to the magnesium nitrate) and distill off the nitric acid, at which point you can react it with any one of a number of calcium salts to yield calcium nitrate.

Chemistry Alchemist - 25-7-2012 at 23:08

Well i was thinking, this reaction works with sodium bicarbonate and hydroxide so why cant it work with calcium bicarbonate. I dont have a good source of H2SO4, only way to buy that is from a brand new car battery which is too expensive at this current time, and i dont have the glass ware to make proper acid, id only be able to make a kinda sucky nitric acid

Lithium - 25-7-2012 at 23:27

at cooler temperatures, calcium formate is more soluble than magnesium formate

http://en.wikipedia.org/wiki/Solubility_table

( at 0 degrees C, Mg formate dissolves 14g per 100mls, whereas Ca formate dissolves 16.1g per 100mmls

oxalic acid reacts with glycerine to form formic acid (which can be distilled off)

http://www.erowid.org/archive/rhodium/chemistry/formic.acid....

calcium formate can also be formed via Ca(OCl)2 and acetaldehyde, which in turn may be formed from Ca(OCl)2 and ethanol

formic acid and CaCO3 react to form calcium formate, CO2 and H2O

[Edited on 26-7-2012 by Lithium]

Chemistry Alchemist - 25-7-2012 at 23:32

Wouldnt mine making Formic acid, it was on my list of things to do for youtube, if i can make all that with out Proper glassware.... id do it

ldanielrosa - 26-7-2012 at 00:57

True calcium hydroxide solubility is low, but magnesium hydroxide solubility is lower per http://en.wikipedia.org/wiki/Solubility_table .

I'm surprised you can't get Ca(NO3)2.4H2O at the agriculture shop.

weiming1998 - 26-7-2012 at 00:57

Quote: Originally posted by Chemistry Alchemist

Wouldnt mine making Formic acid, it was on my list of things to do for youtube, if i can make all that with out Proper glassware.... id do it

I made a video on Youtube about making formic acid using calcium hypochlorite, ethanol and oxalic acid. Yield was about 50 ml of a slightly contaminated, a bit watered-down acid from lots of calcium hypochlorite (no scale) and about 80 ml ethanol (approximate). I'd distil it if I had an efficient distillation setup, but mine was a very crude one involving a rubber tube with a cork on a flat-bottomed flask, that works better as a gas bubbler. You don't actually need very complex equipment; a gas bubbler (which I talked about before, and you can make out of an ordinary glass bottle, cork and a rubber tube) and a few beakers was sufficient. Here is my video that has all the procedures: http://www.youtube.com/watch?v=Bx584hCfWHQ&feature=g-upl

Edit: Thanks for subscribing!

[Edited on 26-7-2012 by weiming1998]

Chemistry Alchemist - 26-7-2012 at 01:15

I subbed to you btw

bbartlog - 26-7-2012 at 18:59

Quote: Originally posted by ldanielrosa

True calcium hydroxide solubility is low, but magnesium hydroxide solubility is lower per http://en.wikipedia.org/wiki/Solubility_table .

Interesting. My first reaction was to think that's hardly useful, since you can't really make up a solution with practical quantities of Ca(OH)2... however, on further thought I recall that metathesis with (somewhat) insoluble inputs has been used industrially. In the 19th century, ammonium sulfate was prepared by filtering aqueous ammonium carbonate through gypsum (in layers supported by canvas). The calcium carbonate is sufficiently less soluble than the calcium sulfate that the reaction proceeds, producing ammonium sulfate and CaCO3.
Similarly, maybe you could run a hot solution of magnesium nitrate through a bed of Ca(OH)2 (held in a coffee filter or the like), repeatedly, until you had achieved sufficient deposition of Mg(OH)2 and dissolution of calcium in solution.

Chemistry Alchemist - 26-7-2012 at 22:22

What about Boiling the 2 together? a very tiny bit of calcium hydroxide is soluble, so what if when that tiny put goes in solution, it reacts to form magnesium hydroxide, and that gives more calcium hydroxide to dissolve?

bbartlog - 27-7-2012 at 04:28

Should work so long as the Ca(OH)2 is a sufficiently fine powder. The bane of such reactions is that the solid phase gets coated with the insoluble product, i.e. if your calcium hydroxide is in larger particles then they'll just get completely covered in magnesium hydroxide and the reaction will come to a halt.

AJKOER - 27-7-2012 at 06:35

Quote: Originally posted by bbartlog

Should work so long as the Ca(OH)2 is a sufficiently fine powder. The bane of such reactions is that the solid phase gets coated with the insoluble product, i.e. if your calcium hydroxide is in larger particles then they'll just get completely covered in magnesium hydroxide and the reaction will come to a halt.

Again the same concept as I noted previously, I would react CaCl2 ( DampRid is a commercially available product) with NH4OH, or better heat impure NH4OH and lead the NH3 gas into a solution of CaCl2. Decant and dilute repeatedly to maintain the Ca(OH)2 as a suspension and to remove the highly soluble NH4Cl impurity. Reaction:

2 NH3 + 2 H2O + CaCl2 --> Ca(OH)2 (s) + 2 NH4Cl

Then, use this very fine suspension of Ca(OH)2 in your proposed reaction with Mg(NO3)2.

[Edited on 27-7-2012 by AJKOER]

bbartlog - 27-7-2012 at 16:43

CaCl2 forms complexes with NH3. If you think about it, it's hardly likely that you could react a very slightly acidic compound (CaCl2) and a weak base (NH4OH) and obtain a more acidic solution (NH4Cl) and a stronger base (Ca(OH)2). I would assume that the reaction runs the other way and that mixing Ca(OH)2 and NH4Cl in solution would result in the production of ammonia, water and CaCl2.

AJKOER - 27-7-2012 at 18:34

bbartlog:

You may be right with completely pure starting chemicals. What I first believed was that anhydrous CaCl2 could undergo a partial (but fully exothermic) hydrolysis with water, for example:

CaCl2 + 2 H2O ---> Ca(OH)2 (s) + 2 HCl (g)

and the NH3 could move the reaction further to the right by removing any HCl in solution.

[EDIT] However, on further thought, it is more likely that when I actually performed this reaction there was probably some CO2 around (in the tap water or the NH4OH), so the correct chemistry (which works very well by the way) is a follows:

CaCl2 + 2 NH3 + H2O + CO2 ---> CaCO3 (s) + 2 NH4Cl

There is a famous name for this reaction when you substitute Sodium for Calcium, which I will let others expound upon.

Now on your 'complex' comment with NH3, I believe the dry salt CaCl2 (or even the dihydrate CaCl2.2H2O, for example) forms a series of adducts with ammonia: CaCl2.NH3, CaCl2.2NH3, CaCl2.4NH3 and CaCl2.8NH3. The adducts may exist in an aqueous solution, but I do not believe they can be created in an aqueous environment and speculate that they would not play a role in this reaction.

[Edited on 28-7-2012 by AJKOER]