DACA subsatanta este alcatuita numai din H si O, rezulta ca are 88,88%O
100g substanta contine 11,11gH........88,88gO
100g substanta..............11,11/1 atH........88,88g/16 at O
" ".....................................11,11atH.............5,55 at O
DECI, raportul atomic H;O= 2;1 ---> cred ca este H2O