Apparent Molar Volumes and Standard Partial Molar Volumes of Aqueous Sodium Phosphate Salts at Elevated Temperatures
Bibliographic record
Abstract
Densities and apparent molar volumes of aqueous NaH 2 PO 4 (0.1 to 2.1) mol·kg −1, Na 2 HPO 4 (0.1 to 0.5) mol·kg −1 and Na 3 PO 4 (0.4 to 0.6) mol·kg −1 have been determined using a platinum vibrating tube densimeter at temperatures from 473 K to 598 K, 473 K to 570 K, and 373 K to 497 K, respectively, and a pressure of 15 MPa. For the monosodium and disodium phosphate salts, the Pitzer ion-interaction model was used to extrapolate the apparent molar volumes to infinite dilution and to obtain standard partial molar volumes, V °, of NaH 2 PO 4 (aq) and Na 2 HPO 4 (aq). These new results show that predicted values from the Helgeson−Kirkham−Flowers model overestimate V ° for these two species. For the monosodium salt, the difference ranged from 5 cm 3 ·mol −1 at 473 K to 24 cm 3 ·mol −1 at 573 K, and for the disodium salt, the difference was 6 cm 3 ·mol −1 at 473 K and 16 cm 3 ·mol −1 at 570 K. The values for disodium phosphate show evidence of significant contributions from an ion pair, probably NaHPO 4 − (aq). The apparent molar volumes of Na 3 PO 4 (aq) could only be obtained over a narrow range of concentration due to hydrolysis, and consequently it was not possible to determine V ° of the species PO 4 3− (aq) from their concentration dependence.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".