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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:

10th May 2005 and 25th May 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: BS 2000: Part 15 (equivalent to ISO 3016), Method A1 of Commission Directive 92/69/EEC

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of inspection: December 2002; Date of certificate: February 2003

Type of method:

pour point

Melting / freezing pt.:

306 - 312 K

Atm. press.:

other: Ambient

Decomposition:

no

Sublimation:

no

The measured stationary points are shown in the following table:

Measurement	Determination 1	Determination 2
Stationary point (K)	306	306
Pour point (K)	309	309

Mean pour point : 309 ± 3 K.

Discussion:

It was noted that the determined pour point was some way above ambient room temperature (approximately 293 K), whilst the original sample was observed to be a colourless turbid liquid at room temperature. This was considered to be due to the complex mixture of various molecular weight hydrocarbons making up the test material. In the original sample, the lower molecular weight portion would be liquefied, whilst the higher molecular weight portion would remain in a semi-solid suspension/emulsion, giving the sample its turbid appearance. On heating, the sample became clear and colourless as the higher molecular weight portion melted. As this now homogeneous mixture was cooled, the higher molecular weight components would solidify first, effectively “freezing” the sample in a waxy state. When this waxy solid was left overnight in ambient conditions, it remained in this state. However, it was considered that given further time the lower molecular weight portion would begin to slightly solubilise some of the higher molecular weight portion, returning the sample to its original turbid liquid state.

Conclusions:

The pour point of the test material has been determined to be 309 ± 3 K.

Executive summary:

Pour point of 'Paraffin waxes (Fischer-Tropsch), full range, C15-50 - branched and linear':

309 ± 3 K (arithmetic mean of two determinations), using BS 2000: Part 15 (equivalent to ISO 3016), Method A1 of Commision Directive 92/69/EEC.

Description of key information

pour point of the test material (determined using EU Method A.1): 309 ± 3 K (arithmetic mean of two determinations)

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

306 K