Go Back   Chemistry Help Forum > Chemistry Forums > Undergraduate Chemistry Forum

Undergraduate Chemistry Forum Ask your undergraduate chemistry questions here.

Reply
 
Thread Tools Display Modes
Old Oct 29th 2017, 11:49 AM   #1
Oldschool
Junior Member
 
Join Date: Oct 2017
Location: Texas
Posts: 3
Oldschool is on a distinguished road
synthesis of ammonium magnesium phosphate x 6 H2O

Any help appreciated, it's been 37 yrs. since I was in univ. chemistry class.

Trying to flesh out the stochiometric/molar quantities (grams) of magnesium oxide to be combined with monoammoniumphosphate (MAP, a common fertilizer) to create ammonium magnesium phosphate x 6 H2O ?

I'm guessing I can simply heat it the combination in distilled H2O on a magnetic stirrer overnight, then try cooling it to separate by crystals , but I have read that AMP is sparingly soluble in water, so maybe just push pH slightly above 7, cool in fridge, decant and harvest the "sludge" or crystals ?

This substance is a common problem in sewage treatment plants where it precipitates on pipes, as well as kidney stones in humans and dogs.
Oldschool is offline   Reply With Quote
Old Oct 29th 2017, 11:58 AM   #2
Oldschool
Junior Member
 
Join Date: Oct 2017
Location: Texas
Posts: 3
Oldschool is on a distinguished road
reaction should yield simple water, beside mag. ammon. phosphate

Forgot to add:

MAP (NH4H2PO4) is an acidic dihydrogen compound, MO is an alkaline oxide.

Combining the two should yield H2O.
Oldschool is offline   Reply With Quote
Old Nov 6th 2017, 07:03 AM   #3
Oldschool
Junior Member
 
Join Date: Oct 2017
Location: Texas
Posts: 3
Oldschool is on a distinguished road
Answered my own question - - easier than expected

Well, MgO is typically dead burnt magnesium oxide at very highrefractory temps.

I stored the MgO free samples in outdoors in humidity for 10 years, so it's likely absorbed moisture and even Co2 converting it to magnesium carbonate, precise stochiometry isn't much use here.

Fact is MgO and the carbonate are not very soluble in water, whereas MAP is quite soluble.

So, just combine an excess amount of Mg carb. based on it molar stochiometry with the MAP in hot stirred solution (assuming I now have carbonate), allow to react overnight, then decant liquid, through fine filter paper, boil off water to obtain crystals of ammonium magnesium phosphate.

Throw out sludge residue that does not react.

Bingo !
Oldschool is offline   Reply With Quote
Reply

  Chemistry Help Forum > Chemistry Forums > Undergraduate Chemistry Forum



Thread Tools
Display Modes



Facebook Twitter Google+ RSS Feed