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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:

26 Mar 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

GLP compliance:

no

Type of method:

capillary method

Remarks:

and Differential scanning calorimetry

Decomposition:

yes

Decomp. temp.:

>= 182 °C

Remarks on result:

other: atmospheric pressure assumed

Study 1 – Capillary tube in a liquid bath

Observations: In the first run the sample was heated rapidly from RT to 280 °C at approx. 10 °C/min to identify the temperature range for the onset of any thermally induced changes in sample appearance. The sampled remained unaffected up to approx. 180 °C+/- 5 °C as indicated by sample discoloration. However, no melting was observed.

 

In a second run, a fresh sample was pre heated to 160 °C, followed by a controlled bath temperature rise of approximately 3 K/min to 280 °C. Now the onset of discoloration (white to amber) could be identified to be 182 ± 0.3 °C. The sample discoloration increases gradually to a complete blackening indicating an increased charring of the specimen. No melting/boiling was observed in the test range up to 280 °C though.

 

Results and discussions
Melting / freezing point: -
Decomposition: yes
Decomp. temp.: 182 °C

 

Conclusions: The melting point of the test item could not be determined as decomposition was observed starting a temperature of 182.0 ± 0.3 °C.

 

   

Study 2 – DSC

Results and discussion
Melting / freezing point: -
Decomposition: yes

Decomp. temp.: ≥182 °C

The DSC measurement was conducted with a heating rate of 10 K/min showed an endothermal effect in the temperature range 180 - 220 °C, followed by a pronounced exothermal effect in the range of 220-260 °C. However, the remains of the test item were black particles. A mass loss approximately 14% was observed. The shape and nature of the observed thermal events of the heat flow curve indicate the occurrence of decomposition reactions rather than the melting of the test substance.

 

An additional supporting study using a capillary method had been performed in order to examine thermal effects visually and to clarify whether melting occurs. By the capillary method DSC results were confirmed: No melting occurs, instead the substance decomposes before melting.

 

Conclusions:

The substance starts to decompose without melting at 182 °C.

 

Executive Summary: Melting point of Reaction mass of potassium sodium phosphotartrate and potassium sodium tartrate and potassium sodium ortho-phosphate was tested following OECD Guideline 102 using two complementary methods (Differential Scanning Calorimetry and Capillary tube in a liquid bath method). As a result of this test, the melting point of the test item could not be determined as a decomposition was observed starting at a temperature of 182 °C.

 

 

 

 

 

Description of key information

For chemical safety assessment, the experimentally obtained decomposition temperature is used. No melting point could be determined experimentally.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

182 °C

Additional information

decomposition at 182 °C

Epiwin results for CSA:

Melting point: 196.78 °C (calculated for constituent 2) and 90.27 °C (calculated for constituent 1)
Boiling point: 491.45 °C (calculated for constituent 2) and 480.00 °C (calculated for constituent 1)