A father suffered potentially life-changing injuries, and his partner and two-year-old son were also hurt in an acid attack in north London.
The man's injuries are not thought to be life-threatening, but they are life-changing, the Metropolitan Police said.
The man and woman suffered 15% burns to their hands and bodies, while the child was burnt on his face, London Fire Brigade said.
A spokesperson added that the liquid had a pH reading of one, making it a "strong acid and oxidizing substance".
A spokesperson for Scotland Yard said they were called to the scene in Copenhagen Street in Islington, by London Ambulance Service at 1.05pm.
The 40-year-old man, 36-year-old woman, and two-year-old boy were taken to a north London hospital to be treated for injuries "consistent with a noxious substance being thrown".
Enquiries are ongoing and no arrests have been made.