CIRCULAR OF THE NATIONAL BUREAU OF STANDARDS C440 For sale by the Superintendent of Documents, Washington, D. C. Price $2,00 This Circular supersedes National Bureau of Standards Circular No. 12, issued July 6, 1906, and Circular No. 44, issued January 15, 1914, and revised November 1, 1917. The main object of this treatise is to explain the application and manipulation of polarized light for industrial, analytical, and theoretical purposes. The principal application of polarized light is embodied in the many modifications of the polariscope. The increasing applications of polarized light to the arts and sciences has led to a proportionate increase in the requests made to the Bureau for information. In this Circular an attempt is made to answer as far as possible such inquiries as well as furnish information of a broader character and in greater detail than could be given by letter. In order to present the necessary explanations, simple physical conceptions and deductions have been used. Such explanations, however, are not to be construed or interpreted as an explanation of the physical theory of optical activity. In spite of the numerous mathematical treatments of this subject in recent years, and in spite of the important contributions to the subject of the structure of naturally optically active compounds from the chemical viewpoint, a satisfactory explanation of the phenomenon which comprehends existing experimental facts is still lacking. The general subjects of magneto and electro optics in relation to polarized light are not discussed, as they do not come within the province of this treatise. Van't Hoff and Le Bel discovered how to select from substances of known chemical structure those substances which produce an angular rotation of the plane of polarized light. There followed a widespread utilization of the polariscope in the chemical industries and in chemical research. However, despite the voluminous researches which resulted and the fact that physicists have probed deeply into the nature of light in general and polarized light in particular, as well as the nature of the ultimate particles of which all substances are built up, the mechanism of the interaction between polarized light and the structure of optically active substances is still in a state of controversy, as illustrated by the theories of Born, Kuhn, Boys, and others. No attempt therefore has been made to present a picture of the present controversial state of the physical theory of the nature of optical activity. As a justification for the special applications of the polariscope given in this Circular, it may be stated that carbohydrate chemistry, and carbohydrate industry dependent upon carbohydrate chemistry, could hardly have developed to the magnitude it has attained in recent years without the aid and guidance of the polariscope. Conversely, no better insight into the various applications of quantitative measurements with the polariscope can be given than the study of the specific investigations of carbohydrate chemistry. The application of the polariscope in other fields of chemistry, such as essential oils, hydrocarbons, alkaloids, and other optically active substances, will present no difficulties to the chemist familiar with its application in carbohydrate chemistry. Because of this fact, carbohydrate investigations have been given a prominent place in this Circular. The following members of the staff have collaborated in preparing the material for this publication: Frederick Bates, N. L. Bowman, D. H. Brauns, J. F. Brewster, C. S. Cragoe, Harriet L. Frush, P. E. Golden, L. D. Hammond, Mary L. Hubbell, H. S. Isbell, R. F. Jackson, Emma J. McDonald, F. P. Phelps, W. W. Pigman, M. J. Proffitt, J. B. Saunders, C. F. Snyder, and A. Q. Tool. LYMAN J. BRIGGS, Director. CONTENTS PART 1. POLARIZED LIGHT, POLARIMETERS, SACCHARIMETERS, AND ACCESSORY APPARATUS Preface 1. Nature of polarized light.... 2. Inhomogeneity of light and incoherency of light beams 3. Composition of rectilinear oscillations having different 4. Composition of circular oscillations. 5. Polarization by double refraction_. shades- 10. Production of elliptically polarized light (a) By doubly refracting plates. (b) By electric and magnetic fields. III. Measurement of rotation in circular degrees-Continued. 3. Quartz control plates-Continued. IV. Measurement of rotation in sugar degrees. 1. Development of the saccharimeter. (c) Adjustable sensitivity type. 2. Basis of saccharimeter calibration_ (b) The German, or Ventzke, Scale. (c) The International Sugar Scale. 3. Additional constants of the quartz-wedge saccharimeter (a) Rotation ratios for quartz and sucrose solutions. (b) Absolute rotation of normal sucrose solution___ |