hazard, 660 haze horizon in atmospheric chemistry , 660 haze in atmospheric chemistry , 660 health surveillance, 661 heat, , , 661 heat capacity, , 661 heat capacity of activation, , 661 heat flux, , 662 heavy atom effect, 662 heavy atom isotope effect, 662 heavy water, 662 hecto, 662 height equivalent to a theoretical plate in chromatography , 663 height equivalent to an effective theoretical plate in chromatography , 663 helicenes, 663 helicity, 663 heliochromism, 664 helion, 664 helium dead-space in colloid and surface chemistry , 665 helium ionization detector in gas chromatography , 665 helium–cadmium laser, 665 helium–neon laser, 665 helix, 666 helix residue in a polymer , 666 helix sense, 666 Helmholtz energy (function), , 666 hemes (heme derivatives), 666 hemiacetals, 667 hemiaminals, 667 hemiketals, 667 hemileptic [obsolete] , 668 hemins, 668 hemochromes, 668 hemodialysis, 668 hemoglobins, 668 Henderson–Hasselbalch equation, 669 henry, 669