Conductivity, thermal measurements, X-ray investigations, and phase diagram of the Na2S2O7-K2S2O7 system
Bibliographic record
Abstract
The SO 2 oxidation catalyst solvent system Na 2 S 2 O 7 −K 2 S 2 O 7 has been investigated by conductometric, calorimetric, and X-ray methods. The phase diagram has been constructed from the phase transition temperatures measured for totally 23 different compositions. The results agree well with previous thermal investigations. The phase diagram has been calculated from classical thermodynamics using all transition temperatures, the heat of liquid−liquid mixing obtained for 18 different compositions, and previously measured fundamental thermal data for liquid and solid Na 2 S 2 O 7 and K 2 S 2 O 7 . The phase diagram exhibits two eutectics at X K 2 S 2 O 7 equal to 0.4 (mp 615 K) and 0.6 (mp 613 K), respectively, and a maximum at X K 2 S 2 O 7 = 0.5 (mp 619 K) corresponding to formation of the compound NaKS 2 O 7 . This was confirmed by XRD measurements and the crystal structure shown by Rietveld refinement to be triclinic, space group P -1, with a = 5.9050(1) Å, b = 7.2011(1) Å, c = 7.4190(1) Å, α = 101.707(1)°, β = 90.696(1)°, γ = 94.241(1)°, and Z = 2. The crystal structure of K 2 S 2 O 7 was confirmed and the unknown structure of Na 2 S 2 O 7 was similarly shown to be triclinic, space group P -1, with a = 6.8037(1) Å, b = 6.8265(1) Å, c = 6.7846(1) Å, α = 116.361(1)°, β = 95.959(1)°, γ = 84.194(1)°, and Z = 2. It could be excluded that the compound NaKS 2 O 7 was a simple solid solution of the two compounds of the binary system. The measured conductivities in the liquid region of the 18 different compositions have been fitted to polynomials of the form k = A (X) + B (X)( T − T m ) + C (X)( T − T m ) 2, T m = 693 K.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 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".