CLXXV.—Disodium hydrogen phosphate dodecahydrate

Standard enthalpy of formation of disodium hydrogen phosphate hexahydrate and sodium diphosphate

“…As mentioned above, the heat of formation of Na 2 HPO 4 Á6H 2 O has never been previously determined but that of Na 4 P 2 O 7 has been determined by Borisova et al [6] in 1996 (À876.0 ± 4.0 kJ/mol) by using HNO 3 3 mol Á dm À3 as a solvent, Irving and McKerrell [10] in 1968 (À3192.3 ± 4.1 kJ/mol) using a 60% perchloric acid solution and Meadowcroft and Richardson [11] in 1963 (À880.3 ± 10.0 kJ/ mol) using a HCl 6N solution. A considerable divergence is observed but the papers published in 1968 and 1996 reported erroneous values from that of 1963 and 1968, respectively.…”

“…Mixing volumes of E1 and E2 containing the same amount of H 3 PO 4 moles leads to a solution having the mean value acid composition (E3 with 3.77% (w/w) of H 3 …”

“…This compound exists in many hydrated forms. Ghule et al [1], Duval [2], Hammick et al [3] and Wendrow and Kobe [4] showed that disodium hydrogen phosphate dodecahydrate (Na 2 HPO 4 Á12H 2 O) decomposes into (Na 2 HPO 4 Á8H 2 O), (Na 2 HPO 4 Á7H 2 O), (Na 2 HPO 4 Á2H 2 O), (Na 2 HPO 4 Á1H 2 O) and into the anhydrous form.…”

Transition Temperatures of the Hydrates of Na2SO4, Na2HPO4, and KF as Fixed Points in Biomedical Thermometry

“…Of particular significance to biomedical researchers is the gap from 35.36 to 50.664 °C. A literature search for salt hydrate transitions has produced the supplemental list shown in table 2 [31][32][33][34][35][36][37][38]. These systems were considered to have potential as temperature fixed points to fill the gaps in table 1.…”

“…As shown in figure 3, the system Na2HP04: H 2 0 exhibits two incongruent transitions [32,33,40]: one at about 48°C from the heptahydrate to the dihydrate, and the other at about 35 °C from the dodecahydrate to the heptahydrate. At each of these transitions, the behavior of this system should be similar to that of sodium sulfate.…”