I have an update. It doesn't look good.
Here is the email I sent to my chemistry teacher. I'm not expecting a response.
"It looks like my earlier work has been setting me up rather badly for this.
I tested the absorbance of NiCl2 and EDTA using a manual / not a digital / analogue colorimeter. I know I used 0.05M, and my absorbance is averaged at 3.5!
Doing the calibration curve today, with the digital colorimeter, the absorbance of 0.05M NiCl2 was 0.06.
If I plotted the Ni/EDTA on the graph, it would result in a concentration far too high!
Also, I looked at my results today and couldn't believe that I had used CuSO4, as this meant that I should have done a separate calibration curve just for that.
And the results of most of the other complexes seem random, at:
NiCl2 / Oxalic Acid = 0.21M
NiCl2 / conc. Ammonia = 0.14M (and this doesn't take into account whether these concentrations are actually showing the nickel concentration.)
The NiCl2 / conc. Hydrochloric acid was actually perfect, because the maximum absorbance contained no hydrochloric acid at all...
Yeah, I really need to think about what I'm going to do, as at the moment I'm really not sure.
So much for the "simple experiment" that the Salters version promised. "
There's no way to salvage this, is there?