Gravimetric Analysis In Fertilizer

Two types of gravimetric analysis were used in this experiment, precipitation and volatilization. Volatilization and principles of constant weighing were used to determine moisture content of a fertilizer sample. A crucible was brought to constant weight, both while dry and when the fertilizer sample was added. A type of gravimetric analysis, precipitation, was used to determine the percent phosphorus and percent phosphorus pentoxide of the same sample. MgNH5PO4 was precipitated out of the fertilizer sample, and used to compute the percent P2O5, the phosphorus used in fertilizers. This fertilizer sample was found to have 0.929% moisture. Phosphorus content of the sample on a wet basis was 4.388% P and 10.073% P2O5, and on a dry basis, it was

In this experiment, two types of this analysis were used to determine the moisture content and phosphorus content of fertilizer samples. Precipitation gravimetry is characterized by a substance that is precipitated out of the solution and converted into a weighable form. This method was used to determine the moisture content of a fertilizer sample. The second method, volatilization gravimetry, involves the volatilization of a substance from the solution to be once again converted into a form that can be

Source of Error Parameter Affected (+ or -) Error Reduction

Crucible cover opened while transferring crucible Weight of crucible (+), Apparent weight of fertilizer (+); Moisture from air Keep crucible cover closed

Touching the crucible Weight of crucible (+); Moisture from fingers Do not touch the crucible

Touching the fertilizer bottle Weight of crucible (+); Moisture from fingers Always use paper tongs to handle the fertilizer bottle

Crucible weighed while still hot Weight of crucible (-); Warm trapped air weighs less at room temperature Cooling time should be the same

Solution was not stirred well during NH3 addition Particle size of ppt (-); Nucleation would proceed over particle growth, and filtration would be harder Add NH3 slowly, while stirring

Immediate filtration after addition of NH3 Weight of ppt (-); Without digestion, some of the phosphorus would not have time to precipitate yet Allot time for digestion to allow precipitation reaction to proceed to completion

Incomplete drying Weight of ppt (+); Moisture is accounted for in the weight of the ppt Leave the ppt to dry in air and in the oven for the complete amount of time

Conclusions and