I had to do a complexation titration to calculate the concentration of aluminium. In this, 24.9274ml of EDTA was titrated against 0.0111129 M Zn standard solution, which took 39.45 ml of the Zn solution for the colour change.

Next 25 ml of an Aluminium solution was added to a 250 ml flask with 50ml of EDTA before being titrated with the Zn standard again. I got two different volumes for this second step with one being 41.4ml and the other 38.7 ml.

I would appreciate some help in understanding how to calculate the Al concentration from this.