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Dissociation constant

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Description of key information

pKa of H3PO4 at 25 °C:
#1 2.16
#2 7.21
#3 12.32
pKa of H4SiO4 at 30 °C:
#1 9.9
#2 11.8
#3 12
#4 12

Key value for chemical safety assessment

Additional information

Silicon orthophosphate is an inorganic salt, which is a reaction product of silicon oxide/orthosilicic acid and phosphoric acid; the ionic character in water is retained. Therefore the dissociation of silicon orthophosphate is described in terms of dissociation constants for phosphoric acid and silicic acid (handbook data) in a weight of evidence approach. Every reaction step #1 - #4 is related to a dissociation of the consecutive Hydrogen cation.