A - little or no action B - moderate action C - strong action S - unknown FLUID OR MATERIAL CONVEYED NR NBR EPDM HYPALON® Naphta C A C S Naphtalene C C C C Naphtenic acid C B C C Natural gas C A/B C B Neohexane C A/B C S Nickel acetate B B S S Nickel chloride A A A A Nickel nitrate A A A A Nickel sulphate A A A A Nitric acid ? fuming C S C C Nitric acid 10% C S B A Nitric acid 20% C S C B Nitric acid 30% C S C C Nitric acid 40% C S C C Nitric acid 40-60% C S C C Nitrobenzene C S C C Nitrocellulose S S S S Nitrogen gas A A A A Nitromethane B S B C Nitropropane S S S S Nitrous oxide gas A S A A Nonenes C A/B C S