Runaway during neutralization in laboratory

Incident

Batch of ammonia / sulphuric mixture foamed out of control

The Investigation

The stirrer stopped during the addition of ammonia solution to fuming sulphuric acid / product mixture due to a build up of solid in the mixture. The addition completed, and to get mixing to start the thermometer pocket was removed, this allowed the ammonia to penetrate the mixture and react violently.

Follow Up

A training document was produced addressing stirrer failure during processing