Hi Colin. I suggest garden variety glazed porcelain crucibles. They are resistant to acid as long as you do not use HF.

Regards, Deon

Thank you Deon Bezuidenhout, that is quite useful information if I can find a method that uses lower furnace temperatures. Currently I am using methods that require sintering the calcium phosphate in the furnace between 1200 to 1500 Celsius, depending on the method. Unfortunately porcelain coatings will melt at temperatures this high, as will the porcelain itself, as I understand it. I very much appreciate your advice,

-Colin

Dear Colin. Did not know you needed such high temperatures; so gold is also not an option.  Graphite?

Insoluble in water calcium phosphates, such as tetracalcium phosphate, hydroxyapatite, and (alpha- and beta-) tri-calcium phosphate, appear to be soluble in aqueous solutions of EDTA. However, personally, I have not tried this and, therefore, am unable to suggest the proper conditions, such as EDTA concentration, dissolution time, temperature, etc. Presumably, other compounds which able to form stable complexes with calcium could be suitable as well but I know nothing on this point.

Thank you Deon Bezuidenhout and Sergey V. Dorozhkin. You have been most helpful.

Hello Colin

You are pursuing two goals ( you  do not want to use an acid that is too strong, or leave it in the crucible for too long).

Strong acids will do the job sooner but  you can try  racemic lactic acid  that is readily available and inexpensive. It is quite acidic but not too strong. That is what I see for the solvation part.

The second part is you do not want dissolving  to last for ever. That depends on physical properties such as density, porosity, particle size (Kelvin´s equation for surfaces). Since you are heat treating at such high temperatures at the end you are getting a melt or crystals very well sintered. All this means high density (slower dissolution), very low porosity (slower dissolution), one large molten clump in contrast  to small particle size ( and therefore slower dissolution).

What are the options here? To break the melt if possible (not to damage the beloved platinum crucible). You can accelerate by using ultrasound ( not a simple US bath but a US processor)  because it is a difusion process and you have to diminish the Nernst difusion layer thickness. You can achieve this by stirring or by USonicating. Finally you can heat up the mixture of water and lactic acid to shorten the times.

I have not done it, so you have to check if calcium lactate solubility is normal or retrograde so as to decide  wheather to heat or cool down.

A thermal shock could break up melt residue if desired and possible

I hope this gives you some insight

Edgar Delgado

there area a lot of method for  dissolving calcium phosphates in organic acid without damming the crucible,preferably - citric acid,lactic acid and other,the choice and concentration of the acid generally  depends on the characteristic of our study Kinetics or thermodynamic ?

I

Hello

I think that you can use an amino acid with bacteria or amino acid while heating at reflux if you want to avoid the use of an inorganic acid like HCl or HNO3 and to obtain H3PO4 and Ca2+.

Elena Ioakimowa Dyulgerova what are the conditions we need to keep in order mix citric acid with calcium phosphate?. Even i am trying to dissolve calcium phosphate but preferentially in a non polar solvent.