Phase relations of nahcolite and trona at high P-T conditions
Bibliographic record
Abstract
Using cold-seal hydrothermal bomb and piston-cylinder apparatus, we have carried out both forward and reversal experiments to investigate the phase boundary between nahcolite (NaHCO3) and trona (NaHCO3·Na2CO3·2H2O). We found that the temperature of this phase boundary remains low at least up to 10 kbar, so that this phase transformation maintains its univariant nature in our investigated P-T space. The locus of this phase boundary in a log(pCO2)-T space is defined as log(pCO2) = 0.0240(±0.0001)T − 9.80(±0.06) (with pCO2 in bar and T in K), in excellent agreement with earlier 1 atm experiments at different partial pressures of CO2 (pCO2) and theoretical calculation. Using this equation and literature thermodynamic data, the entropy of trona at 298.15 K is constrained to be 303.8 J mol−1 K−1, essentially identical to earlier estimates from different methods. Our experimental results have also been used to constrain the genesis of nahcolite in some fluid inclusions of diverse origins, and it is suggested that nahcolite in these occurrences is most likely a daughter mineral which crystallized from the fluids as temperature decreased, rather than an accidentally trapped phase.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".