A UNIVERSITY student is in a critical condition after a chemical was allegedly thrown in his face.

Emergency services were called to the University of NSW in Sydney's southeast around 6pm Thursday, after two men were involved in a fight inside the chemistry laboratory.

Police allege a 25-year-old man was assaulted with a hammer before a chemical, believed to be sulphuric acid, was thrown on his face.

He was rushed to St Vincent's Hospital, where he remains in a critical condition.

A 26-year-old man was treated for minor burns before being arrested and taken to Maroubra Police Station.

He has been charged with charged with inflicting grievous bodily harm with intent and refused bail to appear in Waverley Local Court today.

Two others were also taken to St Vincent's Hospital, where they were treated for superficial burns, police said.

Police are appealing for anyone with information, who hasn't already spoken to officers to call Crime Stoppers on 1800 333 000.