------------+-----------++------------+--------- Diameter. | Weight. || Diameter. | Weight. ------------------------------------------------ 0.04 inch | 3.6 || 0.015 inch | 0.19 0.035 " | 2.4 || 0.014 " | 0.15 0.03 " | 1.5 || 0.013 " | 0.12 0.025 " | 0.9 || 0.012 " | 0.097 0.02 " | 0.45 || 0.011 " | 0.075 0.019 " | 0.4 || 0.010 " | 0.056 0.018 " | 0.33 || 0.008 " | 0.028 0.017 " | 0.27 || 0.006 " | 0.012 0.016 " | 0.23 || 0.004 " | 0.004 ------------+-----------++------------+--------- The weight of a corresponding button of gold is got by multiplying by 2.25. These figures are based on those given by Plattner, and apply only to buttons of such shape as those left after cupellation. A sphere of silver 0.01 inch in diameter would weigh 0.09 milligram, and a similar sphere of gold weighs 0.167 milligram. It is safer, however, to compare with a micrometer the diameter of the button whose weight has to be determined with that of a standard button of nearly equal size whose weight is known. The weights of the two buttons are proportional to the cubes of their diameters. This plan of working is described more fully in Appendix B., page 440. ~Calculation of the Results.~--After deducting for the silver added, and correcting for the cupellation loss, the calculation is made in the usual way; reporting as so many parts per thousand in the case of rich alloys and as so many ounces and pennyweights, or better as ounces and decimals of an ounce, in the case of poor alloys and ores. In this last case, however, it is less fatiguing to refer to a set of tables which give, either directly or by means of simple addition, the produce corresponding to any weight obtained from certain given weights of the substance. The following table gives the produce in ounces and decimals of an ounce per ton of 2240 pounds:--