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COTTONSEED and other vegetable oils are graded by color, and the color is an important item in deternfining the price which the oil commands on the market. The Bureau of Standards is co6perating with the American Oil Chemists' Society in establishing color standards for this purpose.
However, the reliability of the color grading is not assured merely by providing correct standards. The color sense of the person who does the color grading nmst be considered, especially his ability to perceive small differences in hue for yellows.
At the request of the American Oil Chemists' Society, Mr. Irwin C. Priest of the bureau has conducted tests of the .color sense of about thirty of the society's members; and the results were published in the January number of its official organ, Oil and Fat Industries.
This test was especially designed to measure the observer's ability to perceive small differences at the color which is standard for prime yellow oil. The method of test was that of " right and wrong answers," the observer ,reporting color differences as they appeared to him, while the conductor of the experiment kept a tally of correct and incorrect answers. A score of 9 or IO correct answers in ~o trials indicates that the observer is able to .detect the difference with practical certainty.
The results of these tests, which are regarded as preliminary rather than final, indicate that many of the chemists (perhaps one-third or even two-thirds) are unable to discern with certainty the smallest differences which are considered in color grading the oil in present trade practice. It should be noted, however, that these differences are so small that only exceptional observers can be expected to be certain about them. One or two were found to be quite incompetent to do color grading, being very uncertain about differences which are unmistakable to competent normal observers. At least four fell below what might be reasonably accepted as a normal ability to perceive hue differences.
Incidentally, these tests have shown that the normal observer's * Communicated by the Director.
π SIMILAR VOLUMES
Measurements of the propagation of UHF radio wa¨es in two trapezoidal tunnels are reported. Values of propagation loss in dBr100 m are gi¨en. It is found that the propagation attenuates at least 900 MHz. In addition, a portable FM radio system operating at 900 MHz is tested in one tunnel. It achie¨e