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D1493-97 – Standard Test Method Technical Guide
📐 Scope, Terminology, and Significance
ASTM D1493‑97 defines a general procedure for determining the solidification point of industrial organic chemicals that exhibit an appreciable heat of fusion. The method is applicable within a temperature range of −20 to +150 °C and is intended for relatively pure compounds. Grossly impure samples will produce low results due to component segregation during freezing.
According to Section 3 of the standard, the solidification point is the temperature at which the liquid phase of a substance is in approximate equilibrium with a relatively small amount of the same substance in its solid phase. This empirical constant is distinct from the freezing point defined in Test Method D 1015. Materials specifically detailed in the standard include phenol, naphthalene, phthalic anhydride, and maleic anhydride.
The test method is suitable for setting product specifications and for quality control of industrial organic chemicals. Users are responsible for establishing appropriate safety and health practices; specific hazard statements are located in Section 8 of the standard.
⚙️ Test Procedure and Data Handling
The measurement is performed by cooling a liquid sample under controlled conditions and recording the maximum temperature reached after the initial appearance of a solid phase. The standard permits a choice of certain apparatus alternatives; the specific configuration and selected options must be reported in accordance with Section 12.
For conformance determinations, all observed and calculated values must be rounded “to the nearest unit” in the right‑hand digit of the applicable specification limit, following the rules of Practice E 29. Proper sampling techniques are critical; the standard references Practices D 3437, D 3438, and D 3852 for handling cyclic products, naphthalene, maleic anhydride, phenol, and cresylic acid.
⚠️ Caution on Sample Purity: This test method is applicable only to relatively pure compounds. Values obtained for grossly impure compounds can be significantly low because of the freezing out of one component during the determination.
💡 Key Distinction: Do not confuse the solidification point (D1493) with the freezing point determined by Test Methods D 1015/D 1016. D1493 provides an empirical equilibrium temperature, whereas D1015/D1016 allow an interpretation of mole percent purity from the freezing curve for high‑purity hydrocarbons.
📊 Key Specifications and Reference Data
The following tables summarize the core technical scope of ASTM D1493‑97 and its essential supporting standards.
| 📏 Parameter | 📐 Specification / Application |
|---|---|
| 🔭 Temperature Range | −20 to +150 °C |
| 🧪 Applicable Materials | Most industrial organic chemicals with appreciable heat of fusion |
| 🔬 Key Examples | Phenol, Naphthalene, Phthalic Anhydride, Maleic Anhydride |
| 🎯 Rounding Rule | Per Practice E 29 (to the nearest unit of the specification limit) |
| 📄 Standard Designation | 📋 Title / Purpose |
|---|---|
| D 852 | Companion test method for Solidification Point of Benzene |
| D 1015 / D 1016 | Freezing Points and Purity of High Purity Hydrocarbons |
| E 1 / E 77 | Specification and Verification of ASTM Thermometers |
| D 3438 / D 3852 | Sampling and Handling of Naphthalene, Maleic Anhydride, Phenol, and Cresylic Acid |
❓ Frequently Asked Questions
🔍 What is the temperature range covered by ASTM D1493-97?
The test method covers solidification points between −20 and +150 °C. It is designed for most organic chemicals that exhibit an appreciable heat of fusion within this range.
💡 What is the practical definition of “solidification point”?
It is defined as the temperature at which the liquid phase of a substance is in approximate equilibrium with a relatively small amount of the solid phase. Practically, it is observed as the maximum temperature reached during a controlled cooling cycle after the appearance of a solid phase.
⚡ What is the difference between Solidification Point (D1493) and Freezing Point (D1015)?
The solidification point (D1493) is an empirical constant used for general industrial organic chemicals. The freezing point methods (D1015/D1016) are specific to high‑purity hydrocarbons and allow for calculating mole percent purity based on the freezing point curve. D1493 does not provide a purity calculation.
📌 Can ASTM D1493 be used for impure or crude samples?
No, the standard explicitly states it is applicable only to relatively pure compounds. Values obtained for grossly impure compounds can be low because of the freezing out of one component during the determination, which directly impacts the maximum temperature reading.