Lab 5- Gravimetric Analysis of Phosphorus

What is the equipment/ materials needed for this lab?

• Balance

• 150mL beaker

• Vacuum filtration set up

• Filer paper

• Side -arm vacuum flask

• Glass sir rod 

• Ice bath 

• Graduated cylinders for the following-

• 36.0mL MgSO4 solution

• 15.0mL amonia solution

• isopropyl alcohol

• Wash bottle with DI water

What are the chemicals for this experiment?

• Unknown fertilizer sample (2.0g)

• DI water (20-30 mL for dissolution)

• MgSO4 solution (36 mL)  and ammonia solution (15.0mL)

• Isopropyl alcohol (15mL total for 3 5mL rinses)

How do you Prepare and dissolve the sample and remove the insoluble material?

• weigh out the 2.00 g of fertilizer

• Add the sample to 20-30mL of DI water in a 150mL beaker

• Stir for 5-10 minutes to dissolve

• Vacuum filter the mixture

• Discard the solid, keep the filtrate in the flask

• transfer the contents from the flask into a different beaker and rinse the flask with DI water to prepare it for another use.

How do you precipitate the phosphorus and then crystalize it?

• to the beaker with the filtrate add 36mL of MgSO4 solution to the filtrate and record observations

• add 15 mL of ammonia solution and record observations

• place the mixture in an ice bath for 30 minutes

• while you are waiting the 30 minutes, weigh the dry filter paper

• make sure the DI water is cold when wetting the filter paper

How to collect and dry the precipitate?

• vaccum filter the cold mixture

• rinse the precipitate with cold DI water

• rinse 3 times with 5mL of isopropyl alcohol

• to dry it remove the filter paper + precipitate

• put in the oven