Color Index at www.japanese-home-gardens.com

Rough field classifications employ two principles, color index and grain size. The color index is the proportion of dark-colored, or femic, minerals (olivines, pyroxenes, amphiboles, biotite, iron ores) to light-colored, or salic, minerals (quartz, feldspars, muscovite). Rocks are light-colored, or leucocratic, if the color index is less than 10, mesocratic if it is between 10 and 50, and dark-colored, or melanocratic, if it is more than 50.

If the prism is placed on the Table j spectrometer and the Table rotated, it found that there is a certain position prism with respect to the incident ray for i the angle of deviation is a minimum given color of light. Examination of the ( scale of the spectrometer shows that in thi tion of minimum dernation the incident the emerging ray make equal angles corresponding faces of the prism. The angle of deviation is used in detern index of refraction of a prism for a given] length. If n represents the index of and A the refracting angle of the prisi equation used is.

These two characteristics, in the form of a ratio—LD50/ED50 —comprise what is known as the therapeutic index, a factor of paramount importance in assessing the value of a drug. The higher the therapeutic index, the better the drug, other factors being equal.