The more obvious and likely was the contamination by over-dilution of the known solution. Despite proper laboratory methods, the possibility of excess DI water or remnants of the previous concentration of the solution being retained in the vessels as they were mixed and transferred from pipette to graduated cylinder to glass test tube, is high. Consequently, in order to decrease this in future investigations, it would be advisable to use a separate pipette and graduated cylinder for each of the ten solutions. Other possible sources of error, not necessarily a factor in this experiment, included: utilizing dirty glassware and cuvettes, using tap water which contains contaminating ions, and not calibrating the spectrophotometer/colorimeter. Limitations to this procedure were that the measurement of cobalt in the soil is only theoretical in this instance, as the investigation does not include any actual soil samples. Furthermore, an aqueous solution and heterogeneous mixed solid would not be realistically comparable to the novice chemist, using the spectrophotometer/colorimeter technique. Other possible limitations, not necessarily a factor in this investigation, included: imprecise volume measurements, incorrect molar calculations, and utilizing the wrong prepared cobalt solution (with unknown concentration).
As defined in the lab manual, there was not enough cobalt in the tested soil samples. For