This reference mass is used to calibrate national standards made of platinum-iridium alloy
Experts are willing to make the changes so that it is no longer based on the mass of a solid cylinder of platinum-iridium alloy
that sits beneath three layers of protective glass sealed in a locked vault in Sevres, France.
Among global standards for length, mass, time, and other fundamental quantities, only the kilogram remains a physical object--a carefully machined cylinder of platinum-iridium alloy
at the International Bureau of Weights and Measures at Sevres, France.
Careful recalibration against the so-called international prototype of the kilogram -- a lump of platinum-iridium alloy
that sits in a vault at the International Bureau of Weights and Measures in Sevres, France -- showed the U.