According to a group of scientists from Newcastle University in the United Kingdom, the original kilogram may getting heavier. The International Prototype Kilogram (IPK or Le Grand K, as it is also known), a platinum and iridium cylinder, is the standard kilogram against which all other measurements of mass are set. It was built in 1875 and is stored in the International Bureau of Weights and Measurements in Paris.
Now, Peter Cumpson and Naoko Sano, two investigators from Newcastle University, believe that it may gaining weight. The team of scientists have performed a series of x-ray photoelectron spectroscopy in surfaces similar to the IPK, trying to determine the amount of carbon-based contaminants they contain. The investigators concluded that the contamination caused a slight increase in the surfaces’ weight. The same phenomenon is probably happening to the IPK, the scientists believe. Over time, the IPK may have gained a few micrograms.
Although this may seem insignificant, the truth is that only a few micrograms can have a significant impact in many fields. Besides, the replicas (40 replicas of the IKP where made in 1884 and stored in different locations around the world) may also be suffering from the same phenomenon but at different rates. Because of that, it is probable that currently the kilogram and its replicas have slightly different weights.
The scientists believe that it is possible to remove the contaminants from the IPK by giving it a suntan. They where successful at removing the carbonaceous contaminants from the surfaces they analyzed by exposing them to a mixture of UV and ozone Using the Theta-probe XPS machine.
The article describing the investigation is available in the Journal Metrologia.
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Written by Catarina Loureiro