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Environmental fate & pathways

Hydrolysis

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Description of key information

pH = 2.5; Temp. = 50 ℃; Rate constants for hydrolysis = 4.58 E-5; Half-life = 10.000 - 100.000 h.
The hydrolysis can be ignored in solutions less acidic than pH 4 and at temperatures below 60 ℃.

Key value for chemical safety assessment

Additional information

This data was published in an academic literature, and the method has been detailed in the paper, so it is used as a key study.

At very low pH most of the sulphamate is present as undissociated acid molecules, whereas at high pH the acid exists almost entirely as the free sulphamate ion. Thus, at low pH hydrolysis is rapid, whilst at high pH it is exceedingly slow, so the test was conducted at very low pH and a high temperature.

In the test the titration has been used to figure out the rates of hydrolysis of the sulphamic acid in the pH 1 - 4, and under different temperatures. The hydrolysis rates from pH 1 to 3 with temperatures from 50 to 70 °C have been measured. It was found that abiotic hydrolysis can be ignored at ambient temperature.

Based on this result, it is concluded that no further testing is needed in accordance with the OECD guideline, and sulfamic acid is stable in water at pH 4, 7 and 9 at 25 ºC, with a half-life greater than one year.