The Optical Properties of Organic Compounds
By Alexander N. Winchell
© 1987, McCrone Research Institute, Chicago, IL
“In this day of black-box instrumentation and push-button research, techniques requiring the analyst to think are falling by the wayside. At one time, only 20-30 years ago, some chemists and most mineralogists learned to use the microscope and apply it to optical crystallography.
“Today, almost no chemists and decreasing percentages of mineralogists learn about refractive indices and interference figures. To study theses phase changes and to take advantage of the resulting superior physical properties requires a means of characterization and identifying the different crystal forms. X-ray diffraction is one way to do this but optical crystallography (petrography) is, by far, the best method.
“First, there are many numerical measurements to uniquely characterize a given crystalline phase. Second, these properties are numerically as different for two different polymorphs or solvents of a given compound as they would be for two different chemical substances. Third, given tabulation of crystallographic data the identification of a particular compound and solid phase thereof is very rapid, more rapid than X-ray diffraction. Finally, the confidence of a chemical microscopist in his identification of a given compound and phase is unmatched by users of any other technique. This book is a tabulation of the morphological and optical properties of most of the common organic compounds in daily use.”
— from the Preface to the McCrone Research Institute Edition by Walter C. McCrone