4'-aminoazobenzene-4-sulphonic acid

Endpoint summary

Additional information

Appearance/physical state/colour

On the basis of visual perception and olfactory property, 4'-aminoazobenzene-4-sulphonic acid was found to be a light brown organic amorphous solid with characteristic odor at 37°C and 970 hPa.

Melting point/freezing point

Melting Point of 4'-aminoazobenzene-4-sulphonic acid was estimated to be 196.84°C. The supporting study also indicates the melting point to be 200°C

 

Boiling point

Boiling point of 4'-aminoazobenzene-4-sulphonic acid is was estimated to be 477.42°C.

Density

The density of 4'-aminoazobenzene-4-sulphonic acid by the mass by volume method was found to be 0.602 g/cm³ at room temperature of 37°C.This value when converted at 20°C is equivalent to 1.1137 g/cm³.

Particle size distribution (Granulometry)

The particle size distribution (granulometry) of 4'-aminoazobenzene-4-sulphonic acid by the sieve analysis method was found to be in the range of 75 micrometer to 500 micrometer. Majority of the particles were found to be in the size more than 150 (40.32%) micrometer in size.

Vapour pressure

The vapour pressure of 4'-aminoazobenzene-4-sulphonic acid was estimated to be 0.00000000188 Pa at 25°C by the Modified Grain method.

The vapour pressure value for the chemical safety assessment has been taken as 0.000000002 Pa.

Partition coefficient

The experimental value of octanol water partition co-efficient (log Pow) of 4'-aminoazobenzene-4-sulphonic acid is -0.3516 at temperature 37°C and pH of 3.30. This value indicates that 4'-aminoazobenzene-4-sulphonic acid is moderately hydrophilic in nature.

Water solubility

The experimental value of the water solubility of 4'-aminoazobenzene-4-sulphonic acid was found to be 513 mg/L at 37°C indicating that the chemical is moderately soluble in water.

Solubility in organic solvents / fat solubility

Gravimetric method was used to determine the solubility of the substance in organic solvent. The experimental value of solubility of 4'-aminoazobenzene-4-sulphonic acid in methanol at 37°C was found to be 640 mg/L indicating that the substance is moderately soluble in methanol.Using the Soxhlet/Solvent extraction method the solubility of the substance in Petroleum ether is observed to be 360 mg/L at 37°C, indicating that the substance is moderately soluble in petroleum ether. The solubility value of 4'-aminoazobenzene-4-sulphonic acid in methanol at 20°C is equivalent to a value of 345.945 mg/L.

Surface tension

In accordance with Column 2 adaptation statement of REACH Annex VII, information requirement 7.6, this end point was considered for waiver since surface activity was not a desired property of 4'-aminoazobenzene-4-sulphonic acid.

Flash point

The principle method used to determine the flash point property of the substance is open cup method. According to open cup considerations, 4'-aminoazobenzene-4-sulphonic acid did not show flash point upto 330°C and at atmospheric pressure 970 hPa. This value is equivalent to 344.71°C at 101325 Pa.

Auto flammability

4'-aminoazobenzene-4-sulphonic acid did not catch fire on being exposed to air at room temperature of 37°C and atmospheric pressure of 970 hPa. This indicates that 4'-aminoazobenzene-4-sulphonic acid is not auto-flammable.

Flammability

From the experimental values of flammability, 4'-aminoazobenzene-4-sulphonic acid ignited when the flame of bunsen burner having temperature of 950°C was brought in contact with it. Thus it can be concluded that 4'-aminoazobenzene-4-sulphonic acid is flammable only at high temperature of about 950°C. However since such high temperatures are not found under normal circumstances of transportation and use, 4'-aminoazobenzene-4-sulphonic acid was considered non-flammable for chemical safety assessment. 

Explosiveness

According to theoretical considerations based on chemical structure, 4'-aminoazobenzene-4-sulphonic acid does not possess explosive properties. The reason for this is there are no chemical groups associated with explosive properties in 4'-aminoazobenzene-4-sulphonic acid Thus, as per column 2 of Annex VII this end point was considered for waiver.

Oxidising properties

4'-aminoazobenzene-4-sulphonic acid was found to have mild oxidising property since 371.76 ml of KMnO4 was required for getting the end point of the redox titration for 100 g of 4'-aminoazobenzene-4-sulphonic acid. This oxidation potential was not considered strong enough for for classifying the chemical as an oxidising solid.Thus, the chemical is considered as non-oxidising for the purpose of chemical safety report and classification.

Stability in organic solvents and identity of relevant degradation products

4'-aminoazobenzene-4-sulphonic acid was found to be stable in organic solvent dichloro methane and no degradation products were formed after 24 hours as evident from the GC-MS chromatogram obtained at 0 hours and that obtained after 24 hours.

pH

1% by volume solution of 4'-aminoazobenzene-4-sulphonic acid was found to exhibit a pH of 3.52 at 25°C. Thus 1% by volume solution of 4'-aminoazobenzene-4-sulphonic acid is acidic in nature.

Dissociation constant

The experimental pKa value for 4'-aminoazobenzene-4-sulphonic acid was found to be 0.00000251 at 37°C.This pka value when converted at 20°C is equivalent to 0.00000135.

Viscosity

This end point was considered for waiver since viscosity is an inherent property of a liquid that offers resistance to its flow and 4'-aminoazobenzene-4-sulphonic acid is a solid substance and hence this testing was considered scientifically unjustified for 4'-aminoazobenzene-4-sulphonic acid.