Reaction mass of l-Glutamic acid, N-coco acyl derivs., disodium salts and l-Glutamic acid, N-coco acyl derivs., monosodium salts

Melting point / freezing point

Description of key information

The melting point of the registered substance, Reaction mass of disodium N-coco acyl-L-glutamate and sodium N-coco acyl-L-glutamate, has been addressed based on read across to the following three analogues:
Sodium N-coco acyl-L-glutamate: Decomposition from 451 K, Walker (2008)
Sodium N-lauroyl-L-glutamate: Decomposition from 456 K, Walker (2008)
Sodium N-myristoyl-L-glutamate: Decomposition with melting from 465 to 504 K, Butler (2008)
All three studies were conducted in accordance with EU Method A.1.
Based on the read across data the registered substance is considered to melt with decomposition from 451 K, based on the lowest observed result.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

451 K

Additional information

The melting point of the registered substance has been addressed using read across to three structurally similar substances, provided as a weight of evidence.

Walker (2008a) determined the melting point of sodium N-coco acyl-L-glutamate using a modified capillary method/ melting temperatures devices with a liquid bath. Under the conditions of the study, the test material was determined to decompose at 458 K and 451 K in determinations 1 and 2, respectively. As a result of the slow, gradual colour change during decomposition, the onset temperatures could only be approximated. DSC testing indicated that the decomposition in the definitive (and preliminary) test was most likely due to thermal processes. During a metal block determination, the dark brown coloured powder (likely a mixture of test material and decomposition product(s)) started to liquefy from approximately 197 °C (470 K). Based on these results, the test material was determined to decompose from approximately 451 K.

Walker (2008b) determined the melting point of sodium N-lauroyl-L-glutamate using a modified capillary method/ melting temperatures devices with a liquid bath. Under the conditions of the study, the test material was determined to decompose at 458 K and 456 K in determinations 1 and 2, respectively. As a result of the low rate of colour change during decomposition, the onset temperatures could only be approximated. DSC testing indicated that the decomposition in the definitive (and preliminary) test was most likely due to thermal processes. During a metal block determination, the dark brown coloured powder (likely a mixture of test material and decomposition product(s)) started to liquefy from approximately 215 °C (488 K). Based on these results, the test material was determined to decompose from approximately 456 K.

Butler (2008) determined the melting point of sodium N-myristoyl-L-glutamate using a modified capillary method/ melting temperatures devices with a liquid bath. The test material went through several stages of physical change during the liquid bath test. Observations from determination 2 indicated the following; the test material became waxy at approximately 370 K, start of decomposition with melting indicated by discolouration and shrinkage started at approximately 465 K and end of decomposition with melting was at approximately 504 K.

A preliminary DSC test performed under air and nitrogen atmospheres indicated that no oxidative decomposition occurred. The thermograms showed an endotherm with a peak at approximately 90 °C corresponding to the test material becoming waxy and a broad endotherm starting at approximately 200 °C corresponding to decomposition with melting. The DSC thermogram was consistent with the observations made in the liquid bath experiment.

The test material was determined to decompose with melting from 465 to 504 K.

All three studies were performed under GLP and in line with the standardised guideline EU Method A.1, and were reported with sufficient detail to assess the reliability of the submitted data. Accordingly they were assigned a reliability score of 2 in line with Klimisch (1997).

Based on the read across data the registered substance is considered to melt with decomposition from 451 K, based on the lowest observed result.