If an element has several compound with other same or different elements of known atomic mass then the compound that has minimum presence of former element indicate the atomic mass of former element.
Procedure
(i) First of all the molecular mass of all compounds known by applying V.D × 2 = mol. weight
(ii) By analysis the presence of the desired element in each compound is known.
(iii) The mass that is lowest among all the compound indicate the atomic mass of that element.
