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Physical & Chemical properties

Boiling point

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Description of key information

Liquid: The substance is a 25% solution in water, therefore performing a study is scientifically unjustified since the boiling point of sodium polysulfide solution will be the same as the boiling point for water.

Solid: No boiling point was found prior to decomposition.

Key value for chemical safety assessment

Additional information

Solid: The boiling temperature of the test item disodium tetrasulfide (EC no. 215-686-9) was determined according to OECD guideline no. 103 (adopted on July 27, 1995) and EU test method A.2 [Council Regulation (EC) No 440/2008 of 30 May 2008].

In a measurement with differential scanning calorimetry a sample of the test item and a reference material (identical crucible without the test item) are subjected to the same controlled temperature program. The difference in the temperatures of the test item and the reference material is recorded and applying a calibration function converted to a heat flow signal. When the sample undergoes a transition involving a change in enthalpy (endothermic on melting or boiling), that change is indicated by a departure from the base line of the heat flow record. A thermogravimetric measurement was carried out as a preliminary test before the DSC measurements. The DSC measurements were performed twice.

To determine a possible boiling point more precisely a crucible lid with a hole of 50 µm diameter was used in the measurements. The small hole causes the generation of a defined atmosphere at constant pressure inside the crucible and allows measurements at near equilibrium conditions, thus preventing evaporation of the test material before reaching the boiling point. The heat flow curves show two endothermic effects, a smaller peak at 245°C (extrapolated onset temperature at 230°), and a larger peak at 287°C (extrapolated onset temperature at 278°). This indicates probably the melting of two phases. The varying proportions of the two peaks in the two measurements are likely to be due to the inhomogenity of the sample material. Upon further heating, a sharp exothermic peak starts at approx. 560°C, indicating decomposition. The measurements were stopped at this point. The residue was melted and yellow-green discoloured. No boiling point was observed.