Dipotassium oxalate

Melting point / freezing point

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

key study

Study period:

31 Aug - 11 Nov 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other 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)

Version / remarks:

adopted in 2008

Deviations:

no

GLP compliance:

no

Type of method:

differential scanning calorimetry

Atm. press.:

ca. 1 013 hPa

Decomposition:

yes

Decomp. temp.:

138 °C

Remarks on result:

other: 3 individual tests with temperature onsets of 138.1 °C, 138.3 °C and 138.0 °C

Results

1st endothermic effect at 138 °C (ranges: 1st test: 120 - 160 °C, 2nd test:110 -170 °C, 3rd test 105 - 165 °C)

2nd endothermic effect at 390 °C (ranges 1st test 380 - 410 °C, 2nd test 370 - 410 °C)

Mass loss: About 10% of mass loss was detected in all 3 tests

Substance appearance: tests conducted until 400 °C grey powder, for test conducted until 200 °C white powder.

In capillary test running up to 410 °C at approx. 155 °C test item started to discolour at 155 °C, condensate was observed at cool end of the capillary.

The 1st endothermal effect of the DSC experiments can be referred to dehydration of test item the 2nd endothermic point can be phase transition

Reference 2

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Type of method:

other: Scanning Calorimetry, Xray powder diffraction

Decomposition:

yes

Remarks:

Determined by DTA, mass loss 16.6%

Decomp. temp.:

800 K

Decomposition:

yes

Remarks:

Decomposition of phase formed by decomposition at 800K

Decomp. temp.:

> 1 150 - < 1 200 K

At 644 K (DTA) or 662 K (DSC) phase transition between orthorombic δ-phase and tetragonal α-phase occurs. When cooling down phase change (from α to δ-phase) is occuring at lower temperatures than for heating. This shows that the phase change is a kinetically inhibited process with high activation energy. At 800 K (DTA) the oxalate salt decomposes. This is linked with a weight loss of 16%. The potassium carbonate salt, carbon monoxide, carbondioxide and oxygen are formed. At 1200 K (DTA) the carbonate salt decomposes. All the phases were characterized by x-ray powder diffractometry.

Reference 3

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

GLP compliance:

not specified

Decomp. temp.:

> 160 °C

Remarks on result:

other:

Remarks:

Dehydration of monohydrate

Description of key information

Substance decomposes before melting could occur. Decomposition started at ca. 138 °C (OECD 102, DSC).