The Collaborative International Dictionary of English v.0.48:

Colorimetry \Col`or*im"e*try\, n. [See Colorimeter.]
   1. The quantitative determination of the depth of color of a
      substance.
      [Webster 1913 Suppl.]

   2. A method of quantitative chemical analysis based upon the
      comparison of the depth of color of a solution with that
      of a standard liquid.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

colorimetry
    n 1: quantitative chemical analysis by color using a colorimeter
         [syn: colorimetry, colorimetric analysis]