Dear Steve
I would like to add something more regarding the reaction between
orthophosphoric acid(H3PO4)and calcium carbonate (CaCO3). I use mass
spectrometer (GEO 20-20) and react CaCO3 and 100%
orthophosphoric acid at 80 degree Celsius in a readymade online system.
After the reaction we see some white precipitates in some vials while
clear Solutions in some others. I suspect this is due to the formation of
calcium Monophosphate (CaH4P2O8.H2O) and calcium diphosphate (Ca3(PO4)2), the
former goes to dissolved phase while the later is water insoluble. I will
be verry happy if any of the isogeochem members inform me what exactly
happens during the reaction.


Regards
Amzad Hussain
Physical Research Laboratory Ahmedabad
India