Aniline melting point describes a precise physical property that matters for handling, storage, and formulation work. Knowing this value helps chemists, engineers, and safety teams predict behavior under process conditions and avoid hazards related to phase changes.
This article explains the numeric value, test methods, influencing factors, and practical implications for working with aniline. The content is structured to support quick reference and deeper understanding of related topics.
| Property | Value | Test Method | Notes |
|---|---|---|---|
| Aniline melting point | −6.2 °C (21.2 °F) | Capillary tube, slow heating | Reported in major chemical handbooks |
| Boiling point at 1 atm | 184 °C (363 °F) | Distillation | May decompose near boiling point |
| Density at 20 °C | 1.02 g/cm³ | Pycnometer | Slightly above water |
| Solubility in water | 3.6 g/100 mL at 20 °C | Shaking flask method | Increases with temperature |
Handling and Storage Below Melting Point
When aniline is stored near or below −6.2 °C, it can solidify, which affects pumping, metering, and mixing in industrial processes. Understanding this helps designers choose appropriate heating jackets and insulation to keep the material in the liquid state.
Operations below the melting point require careful control to avoid freeze-related blockages and to ensure consistent dosing accuracy for reactions that depend on a stable liquid phase.
Safety Considerations Around Melting Point
Aniline is toxic and can be absorbed through the skin, so handling practices are critical when it transitions between solid and liquid. Managing temperature around the melting point minimizes the formation of aerosols and reduces the risk of accidental exposure during transfers.
Thermal control also limits thermal decomposition that can occur at higher temperatures, supporting safer process conditions and compliance with workplace exposure limits.
Impact of Purity on Thermal Behavior
Commercial grades of aniline may contain water, inhibitors, or residual substrates that shift the observed melting point. Impurities typically depress and broaden the melting range, so purified grades are recommended for studies requiring precise phase data.
Analytical methods such as differential scanning calorimetry can detect these shifts and provide insight into the thermal history and contamination level of the material.
Process Engineering and Temperature Control
Designers account for the aniline melting point when sizing reactors, pipelines, and storage tanks. Adequate trace heating or jacketed vessels are specified to maintain temperatures above the solidification point while avoiding overheating that could promote side reactions.
Temperature control is often integrated with level and flow instrumentation to ensure safe startup, shutdown, and emergency cooling scenarios without unplanned solidification in process lines.
Key Takeaways for Working with Aniline Melting Point
- Aniline freezes at −6.2 °C, so process temperatures should stay above this value to avoid solidification.
- Purity, atmospheric pressure, and heating rate can slightly shift the observed melting point.
- Proper thermal management prevents blockages, ensures consistent dosing, and supports safe handling.
- Reference data from authoritative sources align at approximately −6.2 °C under standard conditions.
- Engineers should specify heating and insulation strategies based on the lowest expected process temperature.
FAQ
Reader questions
What temperature does aniline melt at ambient pressure?
Aniline melts at −6.2 °C (21.2 °F) at standard atmospheric pressure, as documented in reference data and verified by calibrated laboratory methods.
How is the melting point of aniline determined in the lab?
Laboratories typically use a capillary tube method with controlled heating rates to record the onset of melting, often complemented by differential scanning calorimetry for confirmation.
Will impurities raise or lower the melting point of aniline?
Most impurities lower the melting point and widen the melting range, which is why purified aniline is preferred when accurate thermal data are needed for research or quality control.
Why does the melting point matter for industrial handling of aniline?
Knowing the melting point informs the design of heating systems, pipe tracing, and storage protocols to prevent solidification, ensure reliable flow, and reduce exposure risk during manual operations.