▁certain ▁well - defined ▁proport ions , ▁rather ▁than ▁mixing ▁in ▁just ▁any ▁proportion ; ▁and ▁Antoine ▁Lav ois ier ▁proved ▁the ▁law ▁of ▁conservation ▁of ▁mass , ▁which ▁helped ▁out ▁Dal ton . ▁Care ful ▁study ▁of ▁the ▁actual ▁numerical ▁values ▁of ▁these ▁proport ions ▁led ▁Dal ton ▁to ▁propose ▁his ▁law ▁of ▁multiple ▁proport ions . ▁This ▁was ▁an ▁important ▁step ▁toward ▁the ▁atomic ▁theory ▁that ▁he ▁would ▁propose ▁later ▁that ▁year , ▁and ▁it ▁laid ▁the ▁basis ▁for ▁chemical ▁formulas ▁for ▁comp ounds . ▁ ▁Another ▁example ▁of ▁the ▁law ▁can ▁be ▁seen ▁by ▁comparing ▁eth ane ▁( C 2 H 6 ) ▁with ▁prop ane ▁( C 3 H 8 ). ▁The ▁weight ▁of ▁hydro gen ▁which ▁comb ines ▁with ▁ 1 ▁g ▁carbon ▁is ▁ 0 . 2 5 2 ▁g ▁in ▁eth ane ▁and ▁ 0 . 2 2 4 ▁g ▁in ▁prop ane . ▁The ▁ratio ▁of ▁those ▁weights ▁is ▁ 1 . 1 2 5 , ▁which ▁can ▁be ▁expressed ▁as ▁the ▁ratio ▁of ▁two ▁small ▁numbers ▁ 9 : 8 . ▁ ▁Lim itations ▁The ▁law ▁of ▁multiple ▁proport ions ▁is ▁best ▁demonstrated ▁using ▁simple ▁comp ounds . ▁ ▁For ▁example , ▁if ▁one ▁tried ▁to ▁demonstrate ▁it ▁using ▁the ▁hydro car b ons ▁dec ane ▁( chem ical ▁formula ▁C 1 0 H 2 2 ) ▁and ▁und ec ane ▁( C 1 1 H 2 4 ), ▁one ▁would ▁find ▁that ▁ 1 0 0   gram s ▁of ▁carbon ▁could ▁react