Colour Measurement Committee

AG (now Datacolor International) software. Finally, the Colour Measurement Committee (CMC) of the Society of Dyers and Colourists in the United Kingdom made some compromises and published a formula based on the J P Coates work but incorporating the CIELAB coordinates [53], This was made a British standard (BS 6923) and soon was adopted by textile associations around the world. The usefulness of such an equation has been demonstrated many times in the textile industry and in some papers from manufacturers of textured, molded polypropylene as well. 

There are other minor nonequivalencies of ISO test procedures compared to ASTM standards, but for color difference the ISO Test Procedure No. 105 is unique. Those who use Colour Measurement Committee (CMC) procedures—particularly CMC 2 1 Lightness to Color ratio—claim that it facilitates a uniform description for acceptability decisions that is better than any other system in existence. These equations permit the use of a single number tolerance, DEcmc, in a nearly uniform color space. The CMC formula is a modification to the perceptibility CIELAB formula. It is fully described elsewhere in this book, but it deserves some brief notice here because, after all, it is an ISO procedure. The CMC developed the basic British Standard No. 6923, Calculation of Small Color Differences. Soon afterward, in 1989, the American Association of Textile Chemists and Colorists (AATCC) adopted AATCC Test Method 173, CMC Calculation of Small Color Differences for Acceptability. Ford Motor Company indicated a preference for using CMC 2 1 ratio color difference for plastics weathering data for plastics interior trim materials. 

In 1994 following extensive studies by the Colour Measurement Committee (CMC) the CIE94 total colour-difference was defined. In the equation, lightness, chroma and hue are weighted and corrected to account for variation in perceived colour magnitude and for sensitivity and variation in experimental conditions. Recently, the most prominent UK workers in the area of colour equation development combined under a technical committee to determine a generalised and reliable formula (Luo et al. 2000). They have also come up with an equation... 

This analyser is a computer-controlled automated batch analyser, using a stop-flow principle to analyse for pH, conductivity, turbidity and colour. TTie principle of analysis for each module is based on the recommended methods as detailed in the Examination of Waters and Associated Materials issued by the Standing Committee of Analysts of the Department of the Environment. The temperature of the sample hquid flow is measured in order that temperature-compensated results of pH and conductivity can be quoted. 

The U.S.P. method for stilboestrol which is more specific than the above is based on a method proposed by Goodyear, Hatfield and Marsh. 25 ml of a solution of the sample in 95 per cent ethanol, prepared to contain about 20 /jig per ml, is mixed with an equal volume of dibasic potassium phosphate solution (1 in 55) and the solution, in a quartz cell or tube, is then irradiated in ultra-violet light and its extinction measured at the maximum at about 418 m, when the maximum yellow colour has been developed. The optimum conditions (time of irradiation, distance from source of light and quality of quartz container) for maximum colour development are determined prior to making the determination, using a standard solution of stilboestrol in 95 per cent ethanol, containing 20 /ug per ml, and the stilboestrol content of the sample is determined from a comparison of the extinction of the sample solution with that of the standard solution determined at the same time under these conditions. This method has been adapted by the Analytical Methods Committee of the S.A.C. for determination of small amounts of stilboestrol (about 5 mg per pound) in complex mixtures such as animal feeding-stuffs. 

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