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Melting and Dropping Point Analysis

Comprehensive Melting Point and Dropping Point Guide for Measurement and Performance Verification

Home Expertise Library Melting Point and Dropping Point - Automated Analysis

Comprehensive Melting Point and Dropping Point Guide for Measurement and Performance Verification

Melting point and dropping point determination is one of the oldest and most widely used methods for identifying and testing organic substances. It is simple, fast, and provides a numerical value that can be easily recorded, compared, and classified. Because melting point is highly dependent on purity, it is also an effective way to assess substance quality.

This guide explains the fundamental concepts behind melting point and dropping point determination and their practical use in laboratory testing.

Pure crystalline substances melt at a clearly defined temperature, while impure substances usually show a broader melting range. This shift, known as melting point depression, can provide valuable information about sample purity. Automatic melting point analysis makes use of these properties to deliver reliable, reproducible results for routine laboratory testing.

Many synthetic and naturally occurring materials do not have a sharp melting point. Products such as resins, waxes, greases, fats, polymers, asphalt, tars, and ointments soften gradually over a temperature range instead of melting at one exact temperature.

For these materials, dropping point and softening point analysis is a simple and reliable way to characterize thermal behavior. To obtain comparable results, it is important to use standardized equipment, controlled test conditions, and proper sample preparation.

melting point and dropping point

Melting Point Determination

Melting point is usually determined in glass capillaries with a finely ground sample heated in a controlled furnace. The process is monitored visually and by light transmission, since crystalline substances are opaque in solid form and transparent when melted.

Transmission Method

METTLER TOLEDO MP30, MP55, MP70, MP80 and MP90 instruments use a red transmission light source and a video camera to detect changes in light intensity through the sample. This allows accurate melting point detection and full visual documentation of the melting process

Transmission Method
Pharmacopeia Mode

Pharmacopeia Mode

In pharmacopeia mode, the furnace temperature is measured instead of the sample temperature. This means the reported melting point depends on the heating rate and instrument setup. For this reason, measurements are only comparable when the same heating rate is used.

Thermodynamic Melting Point

To obtain the true thermodynamic melting point, the pharmacopeia value is corrected mathematically. This corrected value is independent of heating rate and allows better comparison between substances. MP70, MP80 and MP90 perform this correction automatically.

Laboraist working in a lab
Sample Preparation

Sample Preparation

Good sample preparation is essential for accurate melting point analysis. The sample should be finely ground and filled into the capillary to a height of about 3 mm or less. Overfilling or coarse particles can trap air bubbles and distort the result.

A capillary filling tool helps prepare and pack samples correctly. It supports consistent filling, easier handling, and more repeatable measurements.

Good vs. Poor Preparation

Poor preparation can cause air bubbles, uneven melting, and unreliable transmission curves. Good preparation results in a uniform sample bed, clear melting behavior, and accurate, repeatable results.

Instrument Calibration and Adjustment

To ensure accurate results, melting point instruments should be calibrated regularly using certified reference substances. If the measured values do not match the certified range, the instrument must be adjusted.

METTLER TOLEDO reference substances are recommended for calibration because they come with certificates, barcode identification, and certified melting point values. A regular calibration check, for example once a month, helps maintain reliable performance.

Standards and Compliance

Melting Point Excellence, Dropping Point Excellence

Melting Point Excellence and Dropping Point Excellence are instruments designed to support compliance with a wide range of international standards and pharmacopeias. They help laboratories perform accurate, traceable, and reproducible thermal analysis in regulated environments.

With standardized workflows, secure data handling, and clear result documentation, these instruments are well suited for quality control, method development, and routine testing.

Their flexible configuration and support for certified reference substances make them a reliable choice for organizations that need to follow industry-specific and regulatory requirements.

For an overview of supported standards and norms, visit: www.mt.com/mpdp-norms

LabX PC Software

LabX PC software connects METTLER TOLEDO instruments in a secure, centralized workflow. It supports devices such as analytical balances, density meters, refractometers, titrators, and MP70/MP80/MP90 melting point instruments.

Workflow Using LabX

With LabX, workflows are controlled from the PC, and results are securely stored in a database that can be archived or restored when needed. The software also provides:

  • A single interface for all connected instruments
  • User management with role-based access
  • 21 CFR Part 11-compliant audit trail
  • Centralized data handling and workflow control

Workflow Using LabX

Melting Point Workflow Integration

LabX supports the full melting point workflow on MP70, MP80 and MP90 instruments in three phases:

1. Pre-measurement

1. Pre-measurement

LabX offers flexible management of reference substances, including lot number and expiry date tracking. Calibration and adjustment records are stored for traceability and ongoing instrument monitoring.

2. Measurement

2. Measurement

LabX includes a graphical method editor that lets users define and visualize the complete workflow. SOP instructions can be displayed directly on the instrument screen, helping reduce errors and guide operators step by step.

3. Post-measurement

3. Post-measurement

After measurement, LabX can automatically compare results with target values or tolerances, identify outliers, and prompt the user for the next action. Reports can be generated from templates and exported as PDF or printed on network printers.

LabX also displays the melting point video and transmission curve together, making result review and post-analysis easier than on a standalone instrument.

Dropping Point

Dropping point determination is used to characterize materials that do not have a sharp melting point, such as resins, fats, waxes, polymers, greases, and tars.

  • These substances usually soften gradually over a wide temperature range.
  • The dropping point is the temperature at which the first drop of molten material falls from a standardized cup under controlled conditions.
  • It is one of the most practical methods for thermal characterization of such products.
  • Standardized equipment and sample preparation are important for comparable results.
  • Manual testing is possible, but it requires continuous visual observation and is prone to operator error.
  • Automatic instruments improve accuracy by using video image analysis.
  • The entire test can be recorded and reviewed later if needed.
  • This provides clear evidence of what happened during the measurement.
  • Some instruments can measure two samples at the same time, which increases throughput and efficiency.
  • If identical samples are tested, the result can also be averaged for better reliability.

Many materials, such as resins, fats, waxes, greases, polymers, asphalt, and tars, do not have a sharp melting point. Instead, they soften gradually over a temperature range. For these materials, dropping point and softening point analysis is a simple and reliable way to characterize thermal behavior.

    DP Excellence Instrument Line

    DP Excellence Instrument Line

    The DP Excellence line includes two compact automatic instruments: DP70 and DP90. Both feature a color touchscreen, the intuitive One Click® interface, and video-based measurement for easy operation and accurate results.

    DP70 Excellence

    The DP70 measures two samples at once from room temperature up to 400 °C. It automatically evaluates the mean result and records the full test video on an SD card.

    Key features:

    • Automatic video-based analysis
    • 2 samples measured simultaneously
    • Storage for up to 60 methods
    • Library for up to 100 reference substances
    • GLP-compliant reporting and PDF export
    • Built-in user management
    • Accessories for accurate sample preparation

    DP90 Excellence

    The DP90 offers the same core features as the DP70, but with an external measuring cell that can be placed in a refrigerator, freezer, or fume hood. This makes it suitable for tests from 400 °C down to -20 °C and for samples that may decompose during measurement.

    Scientist working in a lab

    Unique Detection Principle

    The DP Excellence instruments use automatic video image analysis to detect dropping and softening points directly. This provides:
    • Clear visual documentation of the test
    • Reliable and repeatable results
    • Automatic result evaluation
    • The ability to review the full measurement later

    The system can measure two samples simultaneously, doubling throughput and improving efficiency.

    Dropping and Softening Point Calibration

    To ensure accurate results, dropping point instruments must be calibrated regularly using certified reference substances. Because the sample temperature cannot be measured directly, the instrument checks the furnace temperature and compares it with certified values.

    METTLER TOLEDO reference substances such as benzophenone, vanillin, benzoic acid, and potassium nitrate are recommended for calibration and adjustment.

      Sample Preparation

      Sample Preparation

      Reliable results depend on consistent sample preparation. The DP Excellence accessory box includes tools for

      • preparing solid and liquid samples
      • filling sample cups cleanly and efficiently
      • handling dropping and softening point cups
      • improving repeatability and reducing contamination

      The sample preparation tool supports faster workflow, cleaner filling, and more accurate results. It helps prepare up to four cups at once and is designed to keep the outer cup surface clean.

      Sample Types

      Solid Samples

      Powdered samples should be filled carefully into the cup and compacted evenly. The support disk and funnel make it easier to avoid contamination and overfilling.

      Lubricant Greases

      Grease samples are prepared according to relevant ASTM standards. The cup is filled, excess material is removed, and the sample is shaped for reproducible heat transfer.

      Bitumen, Pitch, and Resins

      These samples are melted, homogenized, and poured into the cup under controlled conditions. Careful preparation helps avoid bubbles and improves repeatability.

      Waxes

      Wax samples are melted slightly above the expected melting point, poured into the cup, and allowed to solidify before measurement.

      Liquids and Low-Temperature Samples

      The DP90 can be used with a refrigerator or freezer for measurements down to -20 °C. This is ideal for edible oils, fats, and other samples that must be cooled before testing.

      Measurement Results

      Testing with edible oils, fats, greases, bitumen, and resins showed excellent accuracy and repeatability. The results confirm that the DP Excellence instruments are well suited for standardized dropping and softening point analysis.

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