Tetrasodium 4-amino-5-hydroxy-6-[[2-methoxy-5-[[2-(sulphonatooxy)ethyl]sulphonyl]phenyl]azo]-3-[[4-[[2-(sulphonatooxy)ethyl]sulphonyl]phenyl]azo]naphthalene-2,7-disulphonate

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:

March 03, 2015 - March 05, 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.1 (Melting / Freezing Temperature)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

Deviations:

no

GLP compliance:

no

Type of method:

thermal analysis

Remarks:

Additionally a measurement with the capillary method was performed to clarify the results of the DSC measurements.

Key result

Decomposition:

yes

Decomp. temp.:

>= 225 - <= 330 °C

Remarks on result:

not determinable

 

Melting point / melting range (DSC measurement)

The DSC measurement in an aluminium crucible with a hole showed a broad endothermal effect in the temperature range of 40 – 200 °C and an exothermal effect in the temperature range of 225 – 330 °C. No further endothermal or exothermal effects were observed up to the final temperature of 500 °C. The results of the DSC measurement are summarized in Table1.

Table1: Melting point (DSC-measurement)

Ident No.	Test item / mg	Final test temperature / °C	Type of effect	Temperature range / °C	Onset / °C	Crucible
34871	9.42	500	endothermal exothermal	40 – 200 225 – 330	not determinable not relevant	Aluminium with a hole

After the DSC measurement with the final test temperature of 500 °C the test item appeared unchanged. A mass loss of about 30 % occurred.

The onset temperature is derived from the intersection of the tangent line with the highest slope of the endothermal peak with the baseline. Because of the unusual shape of the endothermal peak in the temperature range of 40 – 200 °C no clear onset temperature could be determined. Therefore an additional measurement with the capillary method was performed in order to clarify the melting range.

 

Melting point / melting range and boiling point / boiling range (capillary tube in a metal block)

A measurement with the capillary method was performed to clarify the results of the DSC measurements. Since this measurement was performed only as a verifying screening a high heating rate of 10 K/min was chosen. The filling height of the test item was approximately 5 mm. The results are summarised inTable 2.

Table2: Results of the capillary method

No.	Set point / °C	Heating rate / K/min	End point / °C	Remarks
1	30	10	350	approx. 102 °C: beginning of condensate formation, test item unchanged approx. 273 °C: test item darkened (colour change from dark brown into black) up to 350 °C: no further change (test item did not melt or boil)

The capillary method measurement showed a condensate formation that is assumed to result from condensing water, as according to the certificate of analysis the test item contained 7.2 % water. The darkening of the test item at approx. 273 °C indicated a decomposition of the test item. This was in accordance with the exothermal effect observed in the DSC measurement in the temperature range of 225 – 330 °C.

Under consideration of the results from the DSC measurements and the capillary method it was concluded that the test item did not melt under atmospheric conditions up to 500 °C, but decomposed starting around 225 °C.

Conclusions:

The test item did not melt under atmospheric conditions up to 500 °C. The test item decomposed starting around 225 °C.

Executive summary:

Differential scanning calorimetry:

The melting point / melting range was determined by differential scanning calorimetry (DSC). The test item and the reference were heated up from ambient temperature to the final temperature at a constant heating rate (10 K/min) in a defined atmosphere (nitrogen). Aluminium crucibles with a small hole are used as containers for the test item and as empty reference crucible. The quantity of heat absorbed or released was measured and recorded.

The DSC measurement in an aluminium crucible with a hole showed a broad endothermal effect in the temperature range of 40 – 200 °C and an exothermal effect in the temperature range of 225 – 330 °C. No further endothermal or exothermal effects were observed up to the final temperature of 500 °C.

The results of the DSC measurement are summarized in Table1.

 

Table1: Melting point (DSC-measurement)

Ident No.	Test item / mg	Final test temperature / °C	Type of effect	Temperature range / °C	Onset / °C	Crucible
34871	9.42	500	endothermal exothermal	40 – 200 225 – 330	not determinable not relevant	Aluminium with a hole

After the DSC measurement with the final test temperature of 500 °C the test item appeared unchanged. A mass loss of about 30 % occurred.

The onset temperature is derived from the intersection of the tangent line with the highest slope of the endothermal peak with the baseline. Because of the unusual shape of the endothermal peak in the temperature range of 40 – 200 °C no clear onset temperature could be determined. Therefore an additional measurement with the capillary method was performed in order to clarify the melting range.

 

Capillary method:

A measurement with the capillary method was performed to clarify the results of the DSC measurements. The test item is filled into the sample tube at ambient temperature. The sample tube is then inserted into the apparatus. The apparatus has a metal block with electrical heating system for the heating of the tubes. The tube is heated to the set point (start temperature) of the measurement. From the set point the tube is heated with a constant heating rate to the maximum temperature. Since this measurement was performed only as a verifying screening a high heating rate of 10 K/min was chosen. The maximum temperature of the equipment is limited to 410 °C. The filling height of the test item was approximately 5 mm.

The results are summarised inTable 2.

Table2: Results of the capillary method

No.	Set point / °C	Heating rate / K/min	End point / °C	Remarks
1	30	10	350	approx. 102 °C: beginning of condensate formation, test item unchanged approx. 273 °C: test item darkened (colour change from dark brown into black) up to 350 °C: no further change (test item did not melt or boil)

The capillary method measurement showed a condensate formation that is assumed to result from condensing water, as according to the certificate of analysis the test item contained 7.2 % water. The darkening of the test item at approx. 273 °C indicated a decomposition of the test item. This was in accordance with the exothermal effect observed in the DSC measurement in the temperature range of 225 – 330 °C.

Under consideration of the results from the DSC measurements and the capillary method it was concluded that the test item did not melt under atmospheric conditions up to 500 °C, but decomposed starting around 225 °C.

Description of key information

The test substance decomposes prior to melting

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

350 °C

Additional information

The test item did not melt under atmospheric conditions up to 500 °C. The test item decomposed starting around 225 °C.

The theoretical Melting Point was calculated by EpiWin to be 350°C (weighted value) for Chesar calculations.