In this experiment we calculated the weight and % of the sample ,
The gravimetric determination of iron in soluble salt is done by converting all iron to , precipitating as a ferrichydroxide and igniting it to . The solubility of ferrichydroxide is very low and therefore quantitative precipitation can be achieved even in acidic solutions of ph up to 4. However , the precipitate is gelatinous and can not be filtrated through sintered glass crucibles because the pores of the crucibles are easily clogged with these types of precipitate. Therefore the precipitate has to be filtered through a filter paper. If the air oxygen is not sufficent , the compound may change to or even metallic iron by carbon from filter paper or reducing gases thar may firm when washing the filter paper.
5 g sample was added 1 ml Hcl and diluted to 250 ml. Then pulled filter paper and 2-3 drops of was added to this solution. After heating just to boil , 3 drops of methyl orange and was added to the solution. After that the solution solution was allowed to precipitate. When the supernatant was become clear , precipitate was allowed to coalugate an filter pulp for 15-30 minutes. Later the solution filtrated and washed with hot wash liquid .After testing the fresh portion filtrate with the filter paper was folded and put into a crucible.Then the crucible was charred off . After that the crucible was ignited at 800-900 in the furnace and weighed. So the weight of was found.
RESULTS AND CALCULATION :
The volume of sample : 5ml
The density of sample : 60 g/L
The molecular weight of Fe : 55.847 g
The molecular weight of : 159.699 g
The mass of crucible : 12.0746 g
The mass of crucible + sample : 12.15.95 g
The mass of sample : 0.0849 g
In this experiment we calculated the weight and % of iron (III) with gravimetric analysis. We used to oxidize ions into before precipitating the solution. Then we added to make the solution alkali and precipitate reaction is obseved as ; While filtering the solution we washed the precipitate with wash liquid and tested the fresh portion filtrate with to observe ions. Washing to completed when no turbitidy is observed. Then the crucible was put on the bunsen burner with low fire. Low fire because of the carbon from the filter paper may reduce to Fe The result of the experiment may have some errors because of the ions that couldn’t be eleminated.Also carbon atoms from the filter paper may reduce to Fe althoug being careful.So the determined weight may not be only pure .