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 machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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 source (direct Gemma or distilled Codex), 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".