Potassium salts of [hexane-1,6-diylbis[nitrilobis(methylene)]]tetrakisphosphonic acid (4-7 K:1)

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:

Between 21 June 2012 and 02 October 2012.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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

Guideline:

EU Method A.1 (Melting / Freezing Temperature)

Deviations:

no

GLP compliance:

no

Type of method:

differential scanning calorimetry

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 colour 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.

Description of key information

Melting point: The acid form (HMDTMP-H) was observed to undergo thermal decomposition from approximately 200°C (Atwal, 2012). This conclusion is read across to the salt to indicate that HMDTMP (4-7K) will also undergo decomposition when heated.

Additional information

The melting point of the anhydrous form of the parent acid (HMDTMP-H) was determined using a differential scanning calorimetry (DSC) in accordance with EU Method A.1 test method. HMDTMP-H (anhydrous form) was observed to undergo thermal decomposition from approximately 200°C. In addition to the DSC method, a visual assessment was performed by heating an aliquot of HMDTMP-H in a capillary tube from room temperature to 350°C. The visual assessment was performed to assist with the interpretation of the thermographic profiles observed in the DSC. In the visual assessment, HMDTMP-H was also observed to undergo a colour change at approximately the same temperature at which HMDTMP-H starts to melt, i.e. HMDTMP-H undergoes simultaneous melting and decomposition.

This result is read-across to the salt, HMDTMP (4-7K); that the salt will also undergo thermal decomposition when heated. Salts would be expected to melt at a higher temperature than the parent acid, and to decompose on heating.

Melting/freezing point values of -10°C and -15°C were reported for HMDTMP-xK in secondary sources to which no reliability could be assigned; these results likely refer to aqueous solution products.