Experiment (11) Determination of Calcium As Oxalate: Theory
Experiment (11) Determination of Calcium As Oxalate: Theory
Experiment (11) Determination of Calcium As Oxalate: Theory
Procedure:
1- Weigh out accurately 0.5g of A.R. calcium carbonate ( which
has been finely powdered and dried at 110-130C for 1 hour )
into a 400 ml beaker.
2- Add 10 ml of water followed by about 15 ml dilute HCl (1:1).
3- Heat the covered mixture until the solid has dissolved and boil
gently for several minutes in order to expel CO2.
4- Rinse down the sides of the beaker and the cover , dilute to 200
ml then add 2 drops of methyl red indicator.
5- Heat the solution to boiling and add very slowly 50ml of a warm
4% ammonium oxalate solution.
6- Add to the resultant hot solution (about 80C) dilute ammonia
solution (1:1) drop wise and with stirring until the mixture is
neutral or faintly alkaline (color change from red to yellow).
7- Allow the solution to stand without further heating for at least an
hour.
8- After the ptt has settled test the solution for complete
precipitation with a few drops of ammonium oxalate solution.