Thousands of Sydney students are returning to campus after an evacuation triggered by a scare over a potentially explosive crystallised acid.
Three towers at the University of Technology Sydney (UTS), where five thousand people were studying and working, were evacuated about 11am (AEDT) on Thursday after two 250 millilitre vials of crystallised picric acid were discovered.
Bomb squad officers packed the vials containing the highly toxic and corrosive acid in blast-proof containers and are taking them away to be detonated, Fire and Rescue NSW Superintendent Tom Cooper told AAP.
"It's all fixed up now," he said.
The acid was stored in an approved blast-proof cabinet but had been exposed to air, causing it to crystalise and become potentially explosive.
Picric acid is used for making dye, medicine, disinfectants and cleaning products.
It's also used by forensic examiners.
"If a criminal grinds a serial number of a weapon, if you paint this stuff over where they've ground the serial number off it goes through the metal, layer by layer until they can identify the serial number again," Supt Cooper said.
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