Bowman Horace A, Schoonover Randall M, Carroll C Leon
Institute for Basic Standards, National Bureau of Standards, Washington, D.C. 20234.
J Res Natl Bur Stand A Phys Chem. 1974 Jan-Feb;78A(1):13-40. doi: 10.6028/jres.078A.004.
We have determined the density of four pieces of single crystal silicon in terms of universally accepted standards of mass and length. These four objects will be used as a working density standard to which all future density work in the United States will be referred. Using these crystals as standards, NBS can calibrate other objects as density standards for associated laboratories. The work was accomplished with the assistance of an interferometer, developed especially for the task, which measures the diameter of commercially available steel balls. From measured diameters ball volumes are calculated. The volumetric information contained in the balls is transferred to the silicon crystals in a newly designed hydrostatic weighing experiment. We have made three independent density determinations on each of the four crystals, and the presently accepted values of the density of each crystal is the average of the three determinations. The random component of uncertainty (3 standard deviations) of these four averages is 0.7 ppm. The systematic error is estimated to be about 0.7 ppm.
我们已根据普遍认可的质量和长度标准测定了四块单晶硅的密度。这四个物体将用作工作密度标准，美国未来所有密度相关工作都将以此为参照。通过使用这些晶体作为标准，美国国家标准局（NBS）可以为相关实验室校准其他物体作为密度标准。这项工作是在一台专门为此任务开发的干涉仪的协助下完成的，该干涉仪用于测量市售钢球的直径。根据测得的直径计算钢球体积。在一项新设计的静水称重实验中，钢球所包含的体积信息被传递到硅晶体上。我们对四块晶体中的每一块都进行了三次独立的密度测定，目前每块晶体密度的公认值是这三次测定的平均值。这四个平均值的随机不确定度分量（3倍标准差）为0.7 ppm。系统误差估计约为0.7 ppm。
