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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Melting point / freezing point

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Administrative data

Endpoint:
melting point/freezing point
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Study performed according well-known techniques but not under GLP

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2000

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 102 (Melting point / Melting Range)
Principles of method if other than guideline:
Both Thermal Gravimetric Analysis (TGA) and Differential Thermal Analysis (DTA) had been performed in order to obtain complementary information and allowing differentiation between endothermic and exothermic events which have no associated weight loss (e.g., melting and crystallization) and those which involve a weight loss (e.g., degradation).
For Differential Thermal Analysis (DTA), sample was heated from 20°C to 350°C in a closed glass crucible with a heating rate of 3.0 K/min.
For Thermal Gravimetric Analysis (TGA), sample was heated from 20°C to 240°C under inert atmosphere in a open Aluminium Oxide crucible with a heating rate of 3.0 K/min.
GLP compliance:
not specified
Type of method:
thermal analysis

Test material

Constituent 1
Reference substance name:
Oxalic acid dihydrated
IUPAC Name:
Oxalic acid dihydrated
Details on test material:
Oxalic acid dihydrated

Results and discussion

Melting / freezing point
Sublimation:
yes
Subl. temp.:
> 160 °C
Remarks on result:
other: at atmospheric pressure

Any other information on results incl. tables

2 endothermic phenomena have been observed belowin DTA:

-         The first endothermic reaction started at 98 ºC (with a peak at 100 ºC) and has been attributed to loss of water of di-hydrated oxalic acid; this is has been proven via TGA showing a weight loss of 29% corresponding to water content of di-hydrated oxalic acid

-         The second endothermic reaction started atand up to; TGA proved the loss of total remain weight (71%) corresponding to full decomposition of oxalic acid giving off gases and corresponding to sublimation

Applicant's summary and conclusion

Conclusions:
The apparent melting point of di-hydrated oxalic acid is caused by loss of crystal water starting at 98°C with a maximum at 100°C. The anhydrous form of oxalic acid starts sublimation around 160°C.