EMPLOYEE HAD JUST LOOSENED THE HEAL WITH AIR ON THE BOTTOM OF ACID CAR & WAS GETTING READY TO TAKE OFF NIPPLE SO THAT THE ACID HOSE COULD BE ATTACHED. HE FORGOT TO CHECK THAT THE VALVE WAS COM PLETELY CLOSED ON THE CAR & CHECK THE NIPPLE FOR PRESSURE. ACID CAME OUT WHEN THE NIPPLE WAS REMOVED & SPLASHED DOWN HIS LIQUID PROOF COAT SLEEVE & INTO HIS GLOVE & BOOT.