Mathieu,

hot (>200C) and fluoride containing concentrated phosphoric acid is said to etch glass.

Somehow silicon phosphate seems to form, faster with increasing polymerization degree of the acid.

[N.H. Ray, The action of phosphoric acid on glass, J.Non-Cryst Solids 5 (1970), 71.]

This said, I never observed anything odd with glassware preparing my own acid (H3PO4/P2O5, 240 C, overnight) and less in any carbonate digestion.

cheers

Chris

2017-02-23 19:00 GMT+11:00 Mathieu Daëron <[log in to unmask]>:

Dear all,

For years we've been reacting powdered carbonate samples in a common acid bath at 90 degrees C, with a small, spherical glass bead placed over each sample to prevent powder projections. I recently realized that I don't know if these beads are made of soda-lime glass or borosilicate glass.

Does anyone have words of wisdom to share regarding the chemical reactivity of soda-lime glass in hot, pure phosphoric acid over durations of up to 48 hours?

Thanks in advance,

– Mathieu Daëron
Centre National de la Recherche Scientifique
Laboratoire des Sciences du Climat et de l'Environnement

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