The incident happened around 10 p.m. on July 5 near the corner of West 47th Street and Sixth Avene, the New York Police Department said.
In a video tweeted by the NYPD on Tuesday, a shirtless man is seen running behind a man and dousing him with a liquid on the back of his head before running away.
No words were exchange prior to the attack, the NYPD said.
The victim, who owns a jewelry shop in the Diamond District, according to WABC-TV, took himself to Columbia Presbyterian Medical Center the next day.
He was treated for second-degree burns on his back.
The suspect was described as a man about 5 feet, seven inches tall and weighing around 130 pounds. He has brown hair and brown eyes, police said.