Police have charged a man with assault for allegedly throwing acid into another man's face at the University of New South Wales in Sydney.

Emergency services were called to the Kensington campus last night where an argument had broken out between two men inside the chemistry laboratory.

Police say a 25-year-old university student was attacked with a hammer and then had sulphuric acid thrown in his face.

He was taken to the intensive care unit at St Vincent's Hospital where he is in a critical but stable condition.

Two other men who came to his aid suffered superficial burns.

Local police commander Gavin Dengate says a 26-year-old is in custody charged with inflicting grievous bodily harm with intent.

"Extremely brutal. To throw something at another person, knowing it to be acid and throwing it at the face, we will allege is extremely vicious," he said.

"We're still working through the exact cause of it and we have had very good cooperation with the University of New South Wales."

The accused was also treated for minor burns and released from hospital, but has since returned.

He was due to face court today.