Volumetric properties of disodium dihydrogen pyrophosphate aqueous solution from 283.15 to 363.15 K at 101.325 kPa
The purpose of this exploration was to determine the density and volumetric properties of the aqueous solution of Na 2 H 2 P 2 O 7 with the molality varied from 0.08706 to 0.88402 mol·kg −1 measured at temperature intervals of 5 K from 283.15 to 363.15 K at 101.325 kPa using Anton Paar Digital vibrating-tube densimeter. The thermal expansion coefficient ( α ), apparent molar volume ( V Φ ), expansibility ( ϕ E ), and partial molar volume ( V B ) of Na 2 H 2 P 2 O 7 (aq) against temperature and molality have been evaluated from density data. On the basis of Pitzer ion-interaction apparent molar volume theory, the Pitzer single-salt parameters ( β M , X 0 v , β M , X 1 v , β M , X 2 v and C M , X v , MX = Na 2 H 2 P 2 O 7 ), and their correlation coefficients a i of the temperature-dependence formula f ( i , p , T ) = a 1 + a 2 ln( T /298.15) + a 3 ( T − 298.15) + a 4 /(620 – T ) + a 5 /( T − 227) for Na 2 H 2 P 2 O 7 were obtained for the first time. It was revealed that predicted apparent molar volumes agreed well with the experimental values indicating the single salt parameters and the temperature-dependent formula are reliable.
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