Page:Tristimulus specification of the Munsell book of color from spectrophotometric measurements (IA jresv31n1p55).pdf/2

 insoluble ash, size, chemical identification tests, taste, color, and so forth, these being indications of purity or quality. All of the tests except color have been under continuous study by committees entrusted with their revision. Color, on the other hand, presented a different type of problem whose solution was not attempted until 1931. Previously the color terms used in the USP and NF had enjoyed no official definition but contained, among others, such confusing terms as "brownish green" or "blackish white," with seldom any reference to a color chart or standard. In the monograph of a drug, the pharmacognocist describes the colors of the outside and the inside, the colors of the various microscopic elements, and finally, the colors of the identification tests. In each instance, no mention is made of the normality of the observer's color vision [1], or of the conditions of lighting or viewing.

Agitation toward research for the development of a suitable system of color terminology was begun in the twenties by E. N. Gathercoal, then a member of the USP Revision Committee [2]. After the founding of the Inter-Society Color Council, of which he was the first chairman, studies were made of the then existing color systems, and in 1933 the report [3] was submitted which became the basis of the system of color names now known as the ISCC-NBS system of color names [4]. Procedures were developed at the same time for the application of these color names to the description of the colors of crude drugs, powdered drugs, chemicals, liquids, precipitates, microscopic structures, and fluorescent materials [5]. The central notations of the color-name blocks were determined for the application of these color names to the description of the colors of soils [6]. Recently these names have also been used to describe the colors of illuminants, and a description of this method of use is in preparation.

In all of this work, the boundaries of the separate color-name blocks have been specified in terms of the Munsell color standards [7, 8]. It was r ealized early in the project that in order to be placed on a sound basis the individual boundaries must be specified in fundamental terms. The accuracy of the system of color names would then be independent of the existence or stability of the individual system of material color standards, in terms of which the system is used in practice. Since the Munsell color system provided a very satisfactory means of determining which color name best described the color of an object, it was decided to measure the spectral reflectances of all of the color standards in the Munsell Book of Color. The specification of the trilinear coordinates and apparent reflectances of each of the Munsell samples would provide an invariable specification of the color of that sample and thereby of a definite point in the framework of the system by which the relative position of each color name is indicated.

Tristimulus specifications of the Munsell Book of Color have been published by Glenn and Killian [8] and were available for some time before that date. Instead of using the Glenn-Killian data, however, it seemed preferable to define the ISCC-NBS system of color names by way of the Munsell samples actually used in the color-names work. This involved a nominal repetition of the spectrophotometric and colorimetric work carried out by Glenn and Killian, but avoided uncertainties arising out of the possible differences between the respective Munsell samples bearing the same