Pentapotassium bis(peroxymonosulphate) bis(sulphate)

Endpoint summary

Additional information

Appearance/physical state/colour

KMPS is a white, odourless, granular, free-flowing salt/powder.

Melting point/freezing point

Using a linear heating rate of 1 °C/min the test substance was found to decompose before melting and therefore does not possess a melting point under the testing conditions (atmospheric pressure).

Boiling point

The test substance was determined to decompose before boiling. Thus, it does not possess a boiling temperature. A single exotherm reaction was observed in the region 140-200°C, which can be attributed to the decomposition of the sample. An endotherm reaction occurred in the range 235 – 250°C, which corresponds to the melting of the decomposed sample that was observed in the melting point test (see: Sec.: 4.1).

Density

The relative density (D 20/4) of the test substance was determined to be 2.35 at 20°C (mean of two separate tests).

Particle size distribution (Granulometry)

The particle size distribution for particles below 10 µm for two test samples were found to be 0.174 % and 0.101 %, respectively, using a

Beckmann Coulter LS 13 320 (laser diffraction techniques). The LS 13 320 was set up to measure particles between 0.4 - 2000 µm. This range meets the need to determine the percentage volume below 10 µm.

Particles below 10 µm are known to bear a inhalation risk of the test substance.

Vapour pressure

The vapour pressure of the test substance was determined to be < 1.7 x 10-4 Pa at 25 °C.

Partition coefficient

In an experimental study the partition coefficient of the test substance was determined to a log Pow of < 0.3 at 20°C. A dependence on the pH range was not expected.

A calculation of the log Pow was performed for Potassium peroxomonosulfate (CAS# 10058-23-8), but not for KMPS triple salt . The calculation was performed using the programme KOWWIN, Log Octanol-Water Partition Coefficient Program, v1.67 (© 2000 U.S. EPA). Although QSAR models like KOWWIN are not able to robustly estimate log Pow values of inorganic substances, the value provided for Potassium peroxomonosulfate (CAS# 10058-23-8) (log Pow = - 3.9) was in the range expected for inorganic salts.

Water solubility

In an experimental study (see: D_K1WaterSol DPT557/012940 key; Doc. No. 119-001) the overall mean water solubility of the test substance was determined to be 364 g/L (> 28%) at 20°C and pH 1.4 - 1.6 This is carried out through placing an excessive amount of triple salt solution, and the solubility is determined by titration of KHSO5 species in solution. In a different experiment (see: B_K1Watersol 3280-27 key; Doc. No. 119-003) the solubility of the test substance was determined by visual inspection to be 297-357 g/l (25-30 %) at 22 °C. This range was found at the pH values 4, 7 and 9.

The difference in values represents the solubility of the more soluble single salt KHSO5 and not the solubility of the KMPS triple salt. In water the anions of each constituent of the triple salt have independent solubility. The overall solubility is dependent on the least soluble anion which represents 297-357 g/l while the most soluble anion KHSO5 has a solubility of 364 g/L. Nevertheless, these two experimental results are in good accordance, the 364g/L was choose as the key value for the CSA as this could represent the worst case situation. Solubility increases slightly with decreasing pH.

Surface tension

The surface tension of the test substance was determined to be 72.9 mN/m at 23°C (concentration: 1 g/L).

Flash point

The determination of the flash-point according to EU Method A.9 is not applicable as this method refers only to liquid substances, but KMPS is a solid (granular salt/powder).

Auto flammability

The test substance was not found to be a self-heating material per EEC test method A.16 (Commission Directive 92/69/EEC).

Flammability

The test substance did not ignite or propagate combustion. Therefore in its solid form, it is not considered to be "highly flammable" according to the criteria of the directive EU method A.10 (solids). Additionally, no flammablility in contact with water (according the the criteria of the directive EU method A.12 (Flammability in contact with water)) and no pyrophoric abilities (according to the criteria of the directive EU A.13 (solids and liquids)) were determined.

Based on the results of all three studies and taking into account the provisions laid down in Council Directive 67/548/EEC and CLP, the test substance in its solid form is not classified according to 67/548/EEC and CLP (GHS).

Explosiveness

The test substance did not ignite under test conditions and was not found to be sensitive to thermal friction or impact stimuli and therefore has no explosive properties.

Based on the experimental resultsand taking into account the provisions laid down in Council Directive 67/548/EEC and CLP, the test substance does not have to be classified with respect to explosiveness.

Oxidising properties

The test substance was found to have no oxidising properties.

Based on the experimental results and taking into account the provisions laid down in Council Directive 67/548/EEC and CLP, the test substance does not have to be classified with respect to oxidising properties.

Stability in organic solvents and identity of relevant degradation products

The test on stability in organic solvents and identity of relevant degradation products is not applicalble as in accordance with column 2 of REACH Annex IX, this test (required in section 7.15) does not need to be conducted as the test substance is inorganic. KMPS is a is a triple salt comprising potassium peroxomonosulfate (2 KHSO5) potassium hydrogen sulfate (KHSO4) potassium sulfate (K2SO4) and thus inorganic.

Dissociation constant

The dissociation constants of the test substance at 25 °C (reported as the pKa1 and pKa2) were determined to be pKa1 = 2.47 and pKa2 = 7.06 applying the titration method according to OPPTS Test Guideline 830.7370.

Viscosity

A test on viscosity is not applicable as n accordance with column 2 of REACH Annex IX, this test (required in section 7.17) does not need to be conducted as the test substance is solid at room temperature. KMPS is a solid (granular salt/powder).