System of measurement The same is true of quarts, gallons, etc. Six US gallons are a little less than five imperial gallons. The Avoirdupois system served as the general system of mass and weight. In addition to this there are the Troy and the Apothecaries' systems. Troy weight was customarily used for precious metals, black powder and gemstones. The troy ounce is the only unit of the system in current use; it is used for precious metals. Although the troy ounce is larger than its Avoirdupois equivalent, the pound is smaller. The obsolete troy pound was divided into 12 ounces, rather than the
Synthesis of precious metals normal to allow used nuclear fuel to stand for about five years before reprocessing, much of this activity will decay away leaving 4.7 MBq of Rh and 5.0 MBq of Rh. If the rhodium metal was then left for 20 years after fission, the 13.3 grams of rhodium metal would contain 1.3 kBq of Rh and 500 kBq of Rh. Rhodium has the highest price of these precious metals ($25,000/kg in 2015), but the cost of the separation of the rhodium from the other metals needs to be considered. Palladium is also produced by nuclear fission in small percentages, amounting