IN SITU XRD STUDY OF THE THERMAL DECOMPOSITION OF NATURAL ARSENIAN PLUMBOJAROSITE
Bibliographic record
Abstract
The thermal decomposition of arsenian plumbojarosite, Pb 0.59 Fe 3 (AsO 4 ) 0.18 (SO 4 ) 1.82 (OH) 6 , from the Lomo Deltoro mine, Mexico, has been studied using in situ X-ray powder diffraction, combined with thermogravimetric and chemical analyses. The minor arsenic becomes enriched in the crystalline products of decomposition as SO 3 is evolved during heating, and it eventually controls the phases that form. Dehydroxylation at 400°C produces an initially amorphous product from which metastable nanocrystalline β-PbSO 4 and β-Fe 2 O 3 crystallize. With an increasing size of crystallites, these transform to the stable anglesite (incorporating As) and hematite phases. Above 620°C, the arsenian anglesite incorporates Na and Fe from the amorphous component and transforms to a cubic eulytine-type phase, Pb 5 Na 2 Fe(AsO 4 ) 3 (SO 4 ) 3 , plus PbO (litharge). At temperatures in the range 720 to 760°C, the eulytine phase and PbO react to form an apatite-type phase, Pb 5 (AsO 4 ) 2 (SO 4 )O, via an intermediate partially amorphous phase region. The phase assemblage of Pb 5 (AsO 4 ) 2 (SO 4 )O plus hematite is stable to about 860°C, where partial melting occurs. Above 860°C, hematite coexists with an amorphous phase and poorly crystalline lanarkite, Pb 2 O(SO 4 ).
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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 | 0.000 | 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".