A simple colorimetric method for analysis of aqueous phenylenediamines and aniline
Bibliographic record
Abstract
A simple and accurate method has been developed for the field and laboratory analysis of four highly toxic substances found in certain industrial wastes in high concentrations. Trinitrobenzenesulfonic acid (TNBS) was used as a colorimetric reagent for 1,4-phenylenediamine (p-PD), 1,2-phenylenediamine (o-PD), 1,3-phenylenediamine (m-PD), and aniline in phosphate buffer of pH 7.4 to form relatively stable compounds that had high absorbance near 430 nm. With sodium sulfite present in the solution at 2 mmol·L–1 or above, higher extinction coefficients were attained and good linear relationships of absorbance with PDs and aniline concentrations were observed. Test times required to achieve maximum absorbance were 60 min for p-PD and m-PD, 30 min for aniline, and 200 min for o-PD. The reliable quantitation ranges were 2–20 µmol·L–1 for p-PD and m-PD and 2–40 µmol·L–1 for o-PD and aniline with the standard error of the estimates being less than 5% in these ranges. Key words: phenylenediamine, aniline, trinitrobenzenesulfonic acid, colorimetric test method.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.003 |
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".