Author Topic: Regarding P2O5 production  (Read 6594 times)

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  • Guest
Regarding P2O5 production
« on: September 23, 2004, 10:57:00 PM »
It is stated in this document (

), about midway down the page under the heading "White Phosphorus", that the following reaction occurs when Calcium Phosphate and Silicon Dioxide are heated together at high temperatures:

2 Ca3(PO4)2 + 6 SiO2 --> 6 CaSiO3 + P4O10

It also says that when mixed with powder carbon and heated to 1450C, the phosphorus pentoxide reacts further to produce white phosphorus and carbon monoxide.

The question is simply this:  At what temperature does the first step of the reaction occur?  Or is the initial reaction the one which requires such high temps in the first place?

Thanks, SWID.

PostScript: SWID is aware that P2O5 is commercially available for reasonable prices.  He just wants to make his own for fun.  :P


  • Guest
i have often wondered that question myself,...
« Reply #1 on: September 30, 2004, 01:07:00 PM »
i have often wondered that question myself, i.e. at what temp the anhydride comes off, assuming the entropies favorable at standard conditions, id assume it would happen at the sublimination temp of phos anhydride which i believe is like 600C.


  • Guest
« Reply #2 on: September 30, 2004, 07:02:00 PM »
if it was that easy, industry would not bother to make it by burning P in air - much less fuel consumption at the lower temp - yes? and if the oxide formed and sublimed away at 600C, then how would the manufacturers get the white P, which the patent literature says does not begin to form until 1050C, and doesn't form fast until 1400C?


  • Guest
condensing it
« Reply #3 on: October 07, 2004, 03:51:00 AM »
SWID was doing some light thinking about it, and realized the real problem would be capturing your hot, gaseous P2O5.  A high boiling aprotic organic solvent, say xylene, would have to be used.  Otherwise, one might simply set up in a similiar fashion as to produce P4, but simply omitting the carbon dust from the mixture.  Except that some time and thought should probably be given to the apparatus itself, to ensure effecient condensation and minimize hazards such as sudden bursts of gas as well as suck back.  Something to think about, kind of like producing sodium metal and hydrogen peroxide from grocery store sodium bicarbonate.  8)

EDIT: Some more food for thought.
2NaHCO3 ------100C-------> Na2CO3 + CO2 + H2O
Na2CO3 --- >400C---> Na2O + CO2
2Na2O  ---- >400C---> 2Na + Na2O2
Na2O2 + H2O  ----dilute HCl*---> H2O2 + ?

SWID hasn't done the research yet to find out the mechanism (or even the balanced equation  :-[ ) behind the formation of hydrogen peroxide with water and an alkali metal peroxide.  Can someone clairfy?

EDIT2: Oh, the *=any mineral acid will do, according the the MERCK 12th ed., under the entry sodium peroxide.  Also, how would one go about seperating the molten sodium metal from the sodium peroxide solid?