Reaction mass of sodium 3-[[4-[(4-ethoxy-m-tolyl)azo]-1-naphthyl]azo]benzenesulphonate and sodium 3-[[4-[(4-ethoxyphenyl)azo]-1-naphthyl]azo]benzenesulphonate

Melting point / freezing point

Link to relevant study record(s)

Reference

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

key study

Study period:

January from 19 to 29, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

Version / remarks:

1995

Qualifier:

according to guideline

Guideline:

other: OECD guideline 113 (Thermal Stability)

Version / remarks:

1981

GLP compliance:

yes (incl. QA statement)

Type of method:

differential scanning calorimetry

Remarks:

and capillary method

Decomposition:

yes

Decomp. temp.:

290 °C

DSC ANALYSIS

In the temperature range of 50 to 140 °C, a broad endothermic effect was observed. Between 150 °C and 170 °C a second endothermic effect was detected. A third endothermic effect was detected between 280 and 300 °C, which leaded directly to an exothermic effect with an energy release of -400 J/g. In the measurement, the third endothermic effect was overlaid from the exothermic effect starting at approx. 290 °C with an energy release of -310 J/g.

During the heating phase two, respectively three endothermic effects were observed, which can be assigned to a drying of the test item (evaporation of water contained in the test item). The test item showed an exothermic signal starting at 290 °C, which can be assigned to decomposition.

Sample weight / mg	Onset of Effect / °C	Range of effect / °C	Weight loss / mg	Atmospheric pressure / hPa
8.54	65.6	50 – 140 (endo)	2.56	998.3
	149.7	150 – 170 (endo)
	287.3	280 – 300 (endo)
	300	300 – 350 (exo)
7.23	56.5	50 – 120 (endo)	2.02	1010.3
	150.1	150 – 170 (endo)
	290	290 – 330 (exo)

CAPILLARY METHOD

To verify the results of the DSC measurement, three additional measurements with the capillary method were performed in the temperature range of 25 – 350 °C with a heating rate of 10 K/min. According to the observations during the tests with the capillary method, the endothermic effects starting at approx. 50 °C and at 150 °C in the DSC measurements with open crucibles cannot be assigned to the melting of the test item, since the test item did not change its appearance. Since the test item contains 8.5 wt.-% water, it can be assumed, that the first endothermic effect is caused by the drying of the test item. The second endothermic effect observed in the DSC measurements is probably caused by a phase transformation. Starting at a temperature of approx. 260 °C the test item becomes black and starts to decompose. The decomposition was accomplished at a temperature of approx. 290 °C. Due to the fact that a sharp exothermic effect was observed in the DSC measurements starting at a temperature of approx. 290 °C, the effect cannot be associated with a melting or boiling. It can be stated that the test item has no melting point and no boiling point up to its decomposition.

Conclusions:

The substance decomposes before melt (290 °C).

Executive summary:

The substance thermal behaviour was investigated in accordance with OECD guidelines 102 and 113.

The determination of the melting and boiling point of the test item was performed using Differential Scanning Calorimetry (DSC) and confirmed by measurements with the capillary method.

In the temperature range of 50 to 140 °C, a broad endothermic effect was observed. Between 150 °C and 170 °C a second endothermic effect was detected. A third endothermic effect was detected between 280 and 300 °C, which leaded directly to an exothermic effect with an energy release of -400 J/g. In the measurement, the third endothermic effect was overlaid from the exothermic effect starting at approx. 290 °C with an energy release of -310 J/g.

During the heating phase two, respectively three endothermic effects were observed, which can be assigned to a drying of the test item (evaporation of water contained in the test item). The test item showed an exothermic signal starting at 290 °C, which can be assigned to decomposition.

To verify the results of the DSC measurement, three additional measurements with the capillary method were performed: according to the observations, the endothermic effects starting at approx. 50 °C and at 150 °C in the DSC measurements with open crucibles cannot be assigned to the melting of the test item, since the test item did not change its appearance. Since the test item contains 8.5 wt.-% water, it can be assumed, that the first endothermic effect is caused by the drying of the test item. The second endothermic effect observed in the DSC measurements is probably caused by a phase transformation. Starting at a temperature of approx. 260 °C the test item becomes black and starts to decompose. The decomposition was accomplished at a temperature of approx. 290 °C. Due to the fact that a sharp exothermic effect was observed in the DSC measurements starting at a temperature of approx. 290 °C, the effect cannot be associated with a melting or boiling. It can be stated that the test item has no melting point and no boiling point up to its decomposition.

Conclusion

The substance decomposes before melt (290 °C).

Description of key information

The substance decomposes before melt (290 °C).

Additional information

OECD 102/113 - Differential Scanning Calorimetry and capillary method