The limiting conductivity of the borate ion and its ion-pair formation constants with sodium and potassium under hydrothermal conditions
Bibliographic record
Abstract
Frequency-dependent molar electrical conductivities for aqueous solutions of potassium borate, and sodium borate have been measured from ambient to near-critical temperatures and pressures to an accuracy of ±3 percent, using a unique high-precision flow-through AC conductance instrument. The concentration dependence of these conductivities was analyzed with the Turq-Blum-Bernard-Kunz ("TBBK") theoretical model to yield (i) limiting conductivities of the borate ion, λ(0)[B(OH)4(-)], and (ii) ion-pair formation constants, KA, for the species NaB(OH) and KB(OH) from T = 298 K to T = 623 K at a constant pressure p ∼ 20 MPa. The ion-pair formation constants for both borate salts were found to be consistent with previous literature studies at temperatures below 473 K. No significant difference in KA was observed between the species NaB(OH) and KB(OH). As temperature was increased from 473 up to 623 K, the degree of association increased significantly, and was found to be considerably higher than for any other 1-1 electrolyte previously studied. For instance, at 623 K, the association constant log KA[NaB(OH)] = 2.75 ± 0.21 was an order of magnitude higher than log KA[NaCl(0)] = 1.53 ± 0.03, and approximately equal to that of a 2 : 1 electrolyte, log KA[SrCF3SO3(+)] = 2.58 ± 0.06. Deviations in the limiting conductivities from Stokes Law show that the borate ion's unusual "structure making" effect, observed by other workers at sub-ambient conditions, persists up to temperatures above 500 K. The temperature dependence of the Walden product ratio is very different from that observed for other monovalent anions for which experimental data are available over this wide range of temperatures.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 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".