3,4-diaminobenzenesulphonic acid

Melting point / freezing point

Administrative data

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

EU Method A.1 (Melting / Freezing Temperature)

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

GLP compliance:

yes (incl. QA statement)

Type of method:

thermal analysis

Test material

Test material information

Constituent 1

Reference substance name:

3,4-diaminobenzenesulphonic acid

EC Number:

231-274-1

EC Name:

3,4-diaminobenzenesulphonic acid

Cas Number:

7474-78-4

Molecular formula:

C6H8N2O3S

IUPAC Name:

3,4-diaminobenzene-1-sulfonic acid

Details on test material:

Chemical Name (IUPAC): 3,4-diaminobenzenesulfonic acid
Molecular Formula: C6H8N2O3S
CAS-No.: 7474-78-4
Molecular Weight: 188.205 g/mol
Batch No.: N-18326
Purity: 99.8 [%, w/w]
Date of expiry: 15.09.2013
Certificate of analysis: No AZ-009-2011, 11.10.2011

Results and discussion

Melting / freezing point

Melting / freezing pt.:

ca. 286.6 °C

Atm. press.:

ca. 1 013 hPa

Decomposition:

yes

Sublimation:

no

Any other information on results incl. tables

RESULTS AND DISCUSSION

The following table summarize the results of the three DSC tests:

Endothermic effect       Test 1       Test 2       Test 3       Ø2 +3       SD

Onset [°C]                  297.11     286.15      287.13     286.64      0.69

Peak Maximum [°C]   314.38     301.94      302.62     302.28

Endset [°C]               325.29     316.02     317.02     316.52

SD = standard deviation

In all tests, an unsteady endothermic melting peak was observed and the colour of the test item changed to black after each run. Test 1 was performed with a higher heating rate of 10K/min and therefore the endothermic peak was shifted to a higher temperature. Thus, for the tests 2 and 3 the heating rate were changed to 5K/min. Although the test item was cooled down and heated again, the endothermic peak did not appear a second time (test 2 & 3). The loss of the endothermic peak after the first heating cycle, the black colour of the sample after each run and the unsteady peak shape is indicating a decomposition of the test item during the melting process. The onset temperatures of test 2 and 3 were not in the expected precision range of the DSC apparatus ( 0.5°C), which could be explained from the unsteady peak shape. Due to the optimized heating rate, only the results from test 2 and 3 were used to calculate the average melting temperature of the test item. Finally, the onset temperature of the endothermic melting peak will be reported with one and the calculated standard deviation with two decimals.

Melting temperature (onset) of the test item 3,4 -diaminobenzenesulfonic acid:

mp = 286.6 +/- 0.69°C (mp = 559.8 +- 0.69 K)