Stolen from the Kitco Gold Forum. Quote prunggu Member .................................. Some old notes of calculations of mine on common alloyed bullion that I came across that I thought may be remotely useful to someone here: Reference .9999 24k .9990 .9167 22k .9000 21.60k 75% 18k 58.33% 14k 50% 12k 37.5% 9k Specific Gravity AGE 91.67% au + 5.33% cu + 3% ag 916.7 x 0.051759 = 47.4474753 53.3 x 0.111617 = 5.9491861 30.0 x 0.094966 = 2.8489800 1000/56.2456414 = 17.78 Krug 91.67% au + 8.33% cu 916.7 x 0.051759 = 47.4474753 83.3 x 0.111617 = 9.2976961 1000/56.7451714 = 17.62 Centenario 90% au + 10% cu 900.0 x 0.051759 = 46.5831 100.0 x 0.111617 = 11.1617 1000/57.7448 = 17.32 14k Centenario fake (assuming copper) 583.3 x 0.051759 = 30.1910247 416.7 x 0.111617 = 46.5108039 1000/76.7018286 = 13.04 .9999 should be easy as pure au assays itself well in terms of specific gravity. ............................................... redmonster Member Here are some Excel macro formulas I used to track water and air temperature and pressure effects. The biggest factor is the density of water. For instance at 25C it is .997 which would yield density measurements approx .3% high if one just assumed 1.000 for water. Another trick is to use a water surface tension reducer such as the stuff used in dishwashers to reduce spotting. Just a drop in a cup of water works great. Public Function densityWater(Optional temp = 20#) densityWater = 0.999972 * (1 - ((temp + 288.9414) * (temp - 3.9863) ^ 2) / (508929.2 * (temp + 68.12963))) End Function Public Function densityAir(Optional temp = 20#, Optional pressure = 1013#) densityAir = 0.0012 * (1 - (temp - 20) / 293) * ((pressure - 1013) / 1013 + 1) End Function Public Function densityUnknown(weight As Variant, weightInWater As Variant, Optional temp = 20#, Optional pressure = 1013#) densityUnknown = weight * (densityWater(temp) - densityAir(temp, pressure)) / (0.999622 * (weight - weightInWater)) + densityAir(temp, pressure) https://www.kitcomm.com/showthread.php?t=107903 ..................... My commentary on the above: Though the gold might be the same percentage,the different alloys in the coin can make a difference to the density. The temperature of the water can make a difference to the test.(should adjust to 20'c) The smaller the coin ,the more accurate should be the scale. These differences,however,are not major.
