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Melting point / freezing point

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Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Between 21 June 2012 and 02 October 2012.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results. The study report was conclusive, done to a valid guideline and the study was conducted under GLP conditions, however no formal claim of GLP compliance was made.
Qualifier:
according to
Guideline:
EU Method A.1 (Melting / Freezing Temperature)
Deviations:
no
GLP compliance:
no
Type of method:
thermal analysis
Key result
Decomposition:
yes
Remarks:
The test item has been determined to undergo decomposition with melting from approximately 200°C.
Decomp. temp.:
ca. 200 °C
Sublimation:
no

Results

Thermograms and thermographic data for Determinations 1 and 2 are shown in Attachment 1 of this Summary.

The results from the visual assessment are shown in the following table.

 

Table 3.4

Reading Number

Temperature (°C)

Observations

1

160

Test item in capillary tube placed into the metal block; original appearance of the test item is a fine white powder.

2

182

No change in test item appearance.

3

210

Small amount of light brown discoloration present on the test item in the bottom of the capillary tube; the rest of the test item remains a fine white powder.

4

215

The discolored part of the test item present on the bottom of the capillary tube begins to melt and appears to be liquid. Rest of the test item still remains a white powder.

5

220

Remaining white powder begins to shrink in towards the center of the capillary tube.

6

221

Test item appears as a light brown liquid in the bottom of the capillary tube. Small grains of test item present on the side of capillary tube remain as white powder..

7

224

Remaining grains of the test item melt into light brown liquid, remaining on the side of the tube.

8

240

Small bubbles begin to form within the test item liquid.

9

255

Small bubbles now all through the test item liquid.

10

260

Bubbles begin to bubble through the test item. All test item now liquid on the bottom of the capillary tube.

11

262

Small bubbles begin to form within the test item. The test item has risen a small amount in the capillary tube.

12

265

No change.

13

290

No change.

14

320

Test item bubbles faster and liquid test item begins to move up the tube; slight change in test item color to medium brown.

15

325

Test item continues to bubble up the tube; black residue present up the capillary tube.

16

330

Dark brown residue on the bottom of the capillary tube; black residue present up the capilliary tube.

17

340

Test item all black and present up the capilliary tube.

18

350

No change.

Conclusions:
The test item has been determined to undergo decomposition with melting from approximately 200°C.
Executive summary:

The determination was carried out by differential scanning calorimetry (DSC) using a procedure designed to be compatible with Method A1 Melting/Freezing Temperature of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 102 of the OECD Guidelines for Testing of Chemicals, 27 July 1995.

   

Discussion

The visual assessment was carried out to assist with the interpretation of the thermographic profiles. This showed that the test item undergoes a change in color at approximately the same temperature at which the item starts to melt. This indicates that the endotherm which starts from approximately 200°C is due to the test item simultaneously undergoing melting and decomposition.

 

Conclusion

The test item has been determined to undergo decomposition with melting from approximately 200°C.

Endpoint:
melting point/freezing point
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
The salts are produced from the parent acid; [Hexane-1,6-diylbis[nitrilo(methylene)]]tetrakisphos-phonic acid. The read-across is therefore based on the presence of common functional groups in both the acid and the salt . The impurity profile of the salt is expected to be similar to that of the parent acid since the salt is prepared from the acid.
Reason / purpose:
read-across source
Key result
Decomposition:
yes
Remarks:
The test item has been determined to undergo decomposition with melting from approximately 200°C.
Decomp. temp.:
ca. 200 °C
Sublimation:
no

Description of key information

Melting point: The acid form was observed to undergo thermal decomposition from approximately 200°C (Atwal, 2012). This conclusion may be read across to the salt.

Key value for chemical safety assessment

Additional information

A recent, reliable DSC test demonstrates that the anhydrous form of the acid undergo thermal decomposition from approximately 200°C. Salts would be expected to melt at a higher temperature than the acid, and to decompose.