The incident took place on Saturday evening in North East Delhi's Karawal Nagar area when the teenager threw the liquid into the eyes of 11-year-old Upendra Kumar.
"The attack caused irritation and swelling in the eyes of the victim although the skin of his face was not burned. The liquid has been sent for tests to determine what it was," said a police official.
The people present at the spot immediately rushed the boy to a hospital where he was treated.
"He was produced before Juvenile Justice Board which has sent him to remand home," the official added.