▁with ▁ 1 8 . 4 6   gram s ▁of ▁hydro gen ▁to ▁produce ▁dec ane ▁or ▁with ▁ 1 8 . 3 1   gram s ▁of ▁hydro gen ▁to ▁produce ▁und ec ane , ▁for ▁a ▁ratio ▁of ▁hydro gen ▁masses ▁of ▁ 1 2 1 : 1 2 0 , ▁which ▁is ▁hardly ▁a ▁ratio ▁of ▁" small " ▁whole ▁numbers . ▁ ▁The ▁law ▁fails ▁with ▁non - sto ichi ometric ▁comp ounds ▁and ▁also ▁doesn ' t ▁work ▁well ▁with ▁polym ers ▁and ▁o lig om ers . ▁ ▁History ▁The ▁law ▁of ▁multiple ▁proport ions ▁was ▁a ▁key ▁proof ▁of ▁atomic ▁theory , ▁but ▁it ▁is ▁uncertain ▁whether ▁Dal ton ▁discovered ▁the ▁law ▁of ▁multiple ▁proport ions ▁by ▁accident ▁and ▁then ▁used ▁atomic ▁theory ▁to ▁explain ▁it , ▁or ▁whether ▁his ▁law ▁was ▁a ▁hypothesis ▁he ▁proposed ▁in ▁order ▁to ▁investigate ▁the ▁valid ity ▁of ▁atomic ▁theory . ▁ ▁In ▁ 1 7 9 2 , ▁Ber tr and ▁Pel let ier ▁discovered ▁that ▁a ▁certain ▁amount ▁of ▁tin ▁will ▁combine ▁with ▁a ▁certain ▁amount ▁of ▁o xygen ▁to ▁form ▁one ▁tin ▁ox ide , ▁or ▁twice ▁the ▁amount ▁of ▁o xygen ▁to ▁form ▁a ▁different ▁ox ide . ▁Joseph ▁Pr oust ▁confirmed ▁Pel let ier ' s ▁discovery ▁and ▁provided ▁measurements ▁of ▁the ▁composition : ▁one ▁tin ▁ox ide ▁is ▁ 8 7 ▁parts ▁tin ▁and ▁ 1 3 ▁parts ▁o xygen , ▁and ▁the ▁other ▁is ▁ 7 8 . 4 ▁parts ▁tin ▁and