L-cystine dihydrochloride

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:

from 2017-03-22 to 2017-03-30

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.1 (Melting / Freezing Temperature)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

differential scanning calorimetry

Key result

Melting / freezing pt.:

>= 211.36 °C

Atm. press.:

1.013 hPa

Decomposition:

yes

Decomp. temp.:

>= 219.42 °C

Sublimation:

no

Pre-Test for melting range

The observations of the pre-test for the melting range are presented in the following table.

Table 1: Pre-test for melting range

Observations	Temperatures
The test item in the capillary was set in aluminium block.	18.8 °C
Colour was slightly brown and getting darker.	from 190 °C
The bottom part was black, the upper part was brown. The upper part was slightly expanded up to the top.	208 °C
Test item was completely black and expanded up to the top. The Bunsen burner was turned down. The test item melted under decomposition.	215 °C

As composition was observed, the sponsor was contacted and based on the pre-test results, the DSC measurement was performed up to 250 °C.

Security Pre-test for the DSC instrument

The crucible was found visually unchanged after reaching a temperature of 270 °C but black test item came out at the perforated position. The weight was recorded at 45.93 mg.

Calibration

After calibration with indium and zinc the measurement of indium yielded the following values:

Table 2: Values DSC Indium

Expected melting point	Measured melting point	Expected heatflow	Measured heatflow	Assessment
156.6 ± 1.0 °C	156.58 °C	28.45 ± 1.0 J/g	28.42 J/g	OK

The measurement of indium after calibration met the validity criteria.

Based on the observations of the pre-test the first event (endotherm) was indicated as the melting point and the second event was indicated as decomposition of the test item. Two independend determinations were performed.

1. Melting point	in °C	in K
1. Determination	211.15	484.30
2. Determination	211.57	484.72
Mean	211.36	484.51
Standard deviation	0.30	0.30
2. Decomposition	in °C	in K
1. Determination	219.22	492.37
2. Determination	219.62	492.77
Mean	219.42	492.57
Standard deviation	0.28	0.28

Conclusions:

The melting point of the test item was determined to be 211.36 ± 0.30 °C at 1013.25 hPa (mean of two determinations) and the decomposition point was determined to be 219.42 ± 0.28 °C.

Executive summary:

A study was conducted according to OECD TG 102 and Regulation (EC) No. 440/2008 method A.1 to determine the melting point of the test item by using differential scanning calorimetry (DSC). One endothermic event and one exothermic event were detected in the determinations. The endothermic event was considered as the melting point as 211.36 ± 0.30 °C (484.51 ± 0.30 K) at a pressure of 1013.25 hPa. The exothermic event was considered as decomposition point, indicated by colour change, with: 219.42 ± 0.28 °C (492.57 ± 0.28 K). These values are the means of two independent determinations.

Description of key information

The melting point of the test item was determined to be 211.36 ± 0.30 °C at 1013.25 hPa (mean of two determinations) and the decomposition point was determined to be 219.42 ± 0.28 °C.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

211.36 °C

Additional information

A study was conducted according to OECD TG 102 and Regulation (EC) No. 440/2008 method A.1 to determine the melting point of the test item by using differential scanning calorimetry (DSC). One endothermic event and one exothermic event were detected in the determinations. The endothermic event was considered as the melting point as 211.36 ± 0.30 °C (484.51 ± 0.30 K) at a pressure of 1013.25 hPa. The exothermic event was considered as decomposition point, indicated by colour change, with: 219.42 ± 0.28 °C (492.57 ± 0.28 K). These values are the means of two independent determinations (reference 4.2-1).