Law of definite composition states that the elements in a given compound are always combined in the same proportion by mass. This law form the basis for the definition of a chemical compound.
Sieving is a mechanical separation technique which depends on the relative sizes of particles in the mixture.
A mesh is used to discriminate between particle sizes. Particles in the mixture which are larger than the mesh size do not pass through the sieve, hence particles whose size is less than that of the mesh are separated from the rest of the particles in the mixture.
