Around 1:45 p.m. Monday, the man tossed the liquid into a window at the Pay-O-Matic on Broadway in Hamilton Heights and demanded cash while holding a lighter.
The 22-year-old cashier complied, giving him a bag of cash.
Police describe the suspect as a 5’9″ man in his 40s, weighing roughly 150 lbs. He was last seen wearing all dark clothing.
Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS (8477).