Potassium carbamoylcarbamate

Endpoint summary

Additional information

The melting temperature and boiling temperature of potassium allophonate could not be determined as the substances sublimated at 298.3 deg C in a melting point/boiling point test performed using a B545 Melting Point Instrument (LIMS 1934) using the capillary method (Intertek, 2010a). Since potassium allophonate underwent sublimation at 298.3 deg C prior to the onset of melting, it is appropriate to estimate a limit value of the vapour pressure using accepted methods. Therefore, MPBVP v1.43, found in EPIWIN v4.10, was used to estimate the vapour pressure of potassium allophonate (U.S. EPA, 2013). The model estimates a vapour pressure of 1.09E-11 mm Hg (1.46E-09 Pa) at 25 deg C, indicating that this substance is highly non-volatile. This result is expected given the high capacity for hydrogen bonding and the ionic nature of potassium allophonate at environmentally-relevant pH. The relative density of potassium allophonate was found to be 1.8731 - 1.8791 g/cm3 at 20 deg C in a test performed according to European Union (EU) Testing Method A.3 (Intertek, 2010b). In a test performed according to Organisation for Economic Co-operation and Development (OECD) Testing Guideline 110, the particle size distribution (granulometry) of potassium allophonate was determined to be: D_0.05 (the 5th percentile of particle diameter) = 316 µm, D_0.10 = 401.7 µm, D_0.50 = 781.7 µm, and D_0.90 = 1326 µm (PTL, 2012).

The octanol-water partition coefficient (Pow) was investigated in a study performed according to OECD Testing Guideline 117 (ABC Laboratories, Inc., 2011). The test substance was not retained on the High Performance Liquid Chromatography (HPLC) system during the test; therefore, the Pow could not be definitively determined. However, it was inferred to be ≤ -1.08 at 25 deg C, indicating that potassium allophonate strongly partitions in the aqueous phase. The solubility of potassium allophonate was determined according to a test performed according to OECD Testing Guideline 105. Potassium allophonate is soluble at 30.03 %w/w (429,890 mg/L), and considered to be very soluble (i.e., >10,000 mg/L).

Potassium allophonate was found to be non-flammable in a test performed according to EU Testing Method A.10 (Intertek, 2010c). Auto flammability was investigated in a test performed according to EU Testing Method A.16 and the auto flammability temperature was found to be 393 deg C (Intertek, 2010c). Potassium allophonate contains oxygen atoms; however, they are only bonded to carbon and, therefore, a structural analysis indicates that potassium allophonate is not an oxidising solid. A structural analysis also indicates that potassium allophonate does not contain any functional groups associated with explosive properties. Thermal stability (self-heating) testing of potassium allophonate determined that this substance is not thermally unstable for supply or transport (Intertek, 2010c).

Investigations of the acid dissociation constant requires testing of a compound in its most protonated state. The most protonated state of potassium allophonate is allophanic acid (CAS No. 625-78-5), which is positively charged in its triprotic form; therefore, in a study performed according to OECD Testing Guideline 112, the log values of the acid dissociation constants (pKa) were determined to be 5.0 (pKa1), 6.5 (pKa2) and 8.6 (pKa3), indicating that allophanic acid will both neutrally charged and negatively charged at environmental pH (Intertek, 2010d). At pH 7, the Henderson-Hasselbalch equation indicates that 24% of molecules are nonionic and 76% are anionic; therefore, potassium allophonate will primarily behave as an anionic molecule at pH 7.

The particle size distribution of potassium allophonate was tested under cGMP following a test method equivalent to OECD Guideline 110. Particle size distribution was found to range from approximately 125 to 4000 µm and 90% of the particles were determined to be less than or equal to 1326 µm in size.

Testing for the following endpoints is waived in accordance with the Registration, Evaluation and Authorisation of Chemicals (REACH) regulation Annexes, since potassium allophonate is a solid at room temperature: surface tension, flash point and viscosity.

References:

ABC Laboratories, Inc. 2011. Potassium Allophonate: Determination of n-Octanol/Water Partition Coefficient by High Performance Liquid Chromatography (HPLC). Testing laboratory: ABC Laboratories, Inc. 7200 E. ABC Lane, Columbia, MO 65202. Owner Company: Kerr Fire Fighting Chemicals, Ashcroft Rd., Knowsley Industrial Park, Kirby, Liverpool L33 7TS, England. Company study no.: 68014. Report date: 2012-05-14.

Intertek ASG. 2010a. Melting point and boiling point of potassium allophonate by Buchi B545 melting point. Testing laboratory: Intertek ASG. Report no.: 1320994. Owner Company: Kerr Fire Fighting Chemicals. Report date: 2010-11-02.

Intertek ASG. 2010b. Potassium Allophonate Relative Density. Testing laboratory: Intertek ASG. Report no.: 1320994. Owner Company: Kerr Fire Fighting Chemicals. Report date: 2010-09-26.

Intertek ASG. 2010c. Fire and Explosive Characteristic of Potassium Allophonate. Testing laboratory: Intertek ASG. Report no.: 1320994. Owner Company: Kerr Fire Fighting Chemicals. Report date: 2010-11-07.

Intertek ASG. 2010d. Study 1320994 pKa value. Testing Laboratory: Intertek ASG. Report no.: 1320994. Owner company: Kerr Fire Fighting Chemicals. Report date: 2010-09-11.

PTL. 2012. Particle size analysis of one potassium allophonate sample. Testing laboratory: PTL. Report no.: 23484. Owner company: Kerr Fire Fighting Chemicals. Report date: 2012-11-01.

United States Environmental Protection Agency (U.S. EPA). 2013. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.10. United States Environmental Protection Agency, Washington DC, USA.