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In the classical equations for the traction on concentric cylinders by a viscous substance, it is assumed that traction on the top and bottom of the inner cylinder (bob) is negligible in comparison with that on the curved surface. In viscometers of practical dimensions, however, it is necessary to compensate for the end-traction or end-effect by adopting one of several expedients in design or by determining the magnitude of the effect and accounting for it in terms of increased length of bob.In the experiments reported in this paper, the method of multiple bobs has been used, and the variation of endeffect with the following factors studied: (1) radius of bob;(2) clearance between cylindrical surfaces; (3) separation between bottom of bob and cup; and (4) viscosity.The magnitude of the end-effect increases with radius and with clearance. For separations at the bottom greater 1 See, for example, H. Lamb, Hydrodynamics (Cam-

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The gloss or luster of a surface is essentially a subjectively evaluated property which is re lated to the manner in which the surface reflects light falling on it. Although the impression or sensation of glossiness is a matter of common experience, measurement of this property in physical terms and correlation of the measurements with its psychological aspects are extremely difficult. The most satisfactory physical measurement involves the use of a goniophotometer, an instrument which measures the amount of light reflected from a surface at various angles. Curves showing intensity of reflected light vs. the scanning angle exhibit a peak at the so- called specular angle for surfaces rated as being of high gloss. Surfaces of more complex struc ture, such as those of fabrics, show a displacement of maximum reflectance from the specular angle; the displacement is related to the angle of the incident light. The curve shape is char acteristic for different fabrics. This article describes the experimental measurement of reflectance by means of a goniopho tometer for a group of fabrics. The results are presented in the form of curves, computed "gloss indexes" or "gloss numbers," and visual ratings by different observers.

In this paper, we propose to examine the rational foundation for the use of surface active agents in so far as it can be logically correlated with the facts of .surface chemistry. This requires (a) a general view of properties measured a t the air-liquid, liquid-liquid , and solid-liquid interfaces by a variety of experimental methods; (b) an evaluation of factors which affect the validity of such measurements and their interpretation, many of which have been given only scant attention; and (c) a brief survey of important industrial processes and products, where the application of quantitative methods assists, not only in understanding the properties observed, but also aids in planning research and development. ' As examples of the application of the concepts of surface chemistry, there may be mentioned the following: foam formation, which, in its simplest form, represents primarily the air-liquid interface ; emulsification, which is dependent chiefly on relations a t the liquid-liquid interface; dispersion of solids in liquids, which presents the important and complicated case typified by numerous commercial products. Detergency requires a consideration of all three of these main classes of interfaces. It is apparent that no single physical measurement will suffice to define all observed phenomena in these instances, although such an effort has frequently been made.Our point of view seeks a compromise between the imperious demands of the moment and the slow, sure progress to be achieved with sound theory and fundamental data. There is, of course, no choice for the technician supervising factory operations. He must adapt some quick laboratory test, simulating in all details the factory operation to be controlled for output rate and for quality standard. But such tests, regardless of the rationale of their use, cannot be translated into principles, nor is it possible to project the interpretation of such data into other operations.Basic to all the phenomena of the interface is the energy change involved. Ordinarily, a surface active agent is useful because it effecta a Present address: 1-0h.r =. X. Soap and sanitary chemicals IS (12): 26-29, 68. 1948: Po (1): (571) s,tva.nia. a w l , 6748.1844.