How to measure concentrations using emission spectrum? Imagine I am using emission spectroscopy to identify the presence of ions in a solution.

Would it be possible to use the intensity of the spectrum to find the concentration of each ion in the solution?

Probably the intensity is directly proportional to the concentration but there might be some scaling factor that I would need to know to find precise values for the concentration of each ion?
You are correct in your assumption. The scaling factor is determined experimentally, this is typically called the 'calibration curve'. Basically you measure the intensity of known concentrations and fit a line through the points. Perhaps this paper can help:
http://science.sciencemag.org/content/202/4364/183