Crystallization Kinetics of Ultraviscous Acetaminophen by Heat Capacity and Enthalpy Measurements and Diffusion Control
Bibliographic record
Abstract
Crystallization kinetics of ultraviscous acetaminophen has been studied at 308.2, 318.2, and 328.2 K by measuring the heat capacity, C(p), and the heat release in real time up to a period of 2.5 days. C(p) decreases according to an inverted sigmoid-shape curve, and the heat released increases according to a similar shape. The extent of crystallization determined from the two measurements differs, thus indicating that the interfacial liquid's C(p) may be slightly different from that of the bulk liquid. Both the excess C(p) of the liquid over the crystal phase and the corresponding excess enthalpy decrease with decrease in the temperature. The kinetics of crystallization follows the Kolmogorov-Johnson-Mehl-Avrami relation, alpha(cryst)(t) = 1 - exp(-kt(m)). The logarithm of the rate constant, ln k, increases from -40.78 at 308.2 K to -32.85 at 328.2 K, and m from 3.60 to 3.83. The product of k and the calorimetric relaxation time remains constant with changing temperature thus showing that the two are inversely related. This shows that crystallization may be diffusion-controlled in the ultraviscous melt. The C(p) data indicate that slow crystallization of melt produces acetaminophen's (monoclinic) form I. Several effects usually overlooked in the crystallized kinetics formalisms have been described.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".