Calibration curves

The concentration of a dissolved substance is the amount of substance per volume of solution.Construction of a calibration curve is a method used to determine the concentration of a substance in a sample by comparing it to a set of standard samples that contain the substance in known concentrations.

Generally this method is used when there is a straight-line relationship between the concentration and a property that can be measured. A graph is prepared using known samples (standards). The property is measured for the unknown sample, and the concentration can be determined from the graph.

Note that the graph will not necessarily go through the origin (0,0), and that a best fit line is used.

dilution factor =	concentration of diluted
	concentration of original

The set of standards are often prepared by quantitative dilution of a solution of known concentration. The dilution factor is the number by which you must multiply the original concentration to find the diluted concentration. This can be expressed mathematically as shown.

If the original solution is 20% sugar, and the final solution is 10% sugar the dilution factor is 0.5.

dilution factor =	volume of original
	volume of diluted

The dilution factor is also equal to the ratio of the volumes of the original and diluted solutions. Because the diluted solution has a larger volume, it is now in the denominator.

Thus if 10 mL of water is added to 10 mL of 20% sugar, the final volume is 20 mL.
By the ratio of the volumes, the dilution factor is 0.5.
Using this and the original concentration, the concentration of the diluted solution is 10% sugar.