We measure mass in terms of kilogram but where does this measurement come from?
who decides this measurement? How accurate is a kilogram used in one country and which country decides that a mass is 1-kg?
The answer is France decides what 1 kilo actually is; The International Bureau of Weights and Measures (French: Bureau international des poids et mesures) is an international standards organisation, one of three such organisations established to maintain the International System of Units (SI) under the terms of the Meter Convention (Convention du Mètre). The organization is usually referred to by its French initialism, BIPM.
The BIPM was created on 20 May 1875, following the signing of the Metre Convention, a treaty among 51 nations.
- On April 7, 1795, the gram was decreed in France to be “the absolute weight of a volume of pure water equal to the cube of the hundredth part of the meter, and at the temperature of melting ice”.
- Since trade and commerce typically involve items significantly more massive than one gram, and since a mass standard made of water would be inconvenient and unstable, the regulation of commerce necessitated the manufacture of a practical realization of the water-based definition of mass. Accordingly, a provisional mass standard was made as a single-piece, metallic artifact one thousand times as massive as the gram—the kilogram.
- Since 1889 the magnitude of the kilogram has been defined as the mass of an object called the international prototype kilogram, often referred to in the professional metrology world as the “IPK”. The IPK is made of a platinum alloy known as “Pt‑10Ir”, which is 90% platinum and 10% iridium (by mass) and is machined into a right-circular cylinder. The addition of 10% iridium improved upon the all-platinum Kilogram of the Archives by greatly increasing hardness while still retaining platinum’s many virtues: extreme resistance to oxidation, extremely high density (almost twice as dense as lead and more than 21 times as dense as water), satisfactory electrical and thermal conductivities, and low magnetic susceptibility.
- The IPK and its six sister copies are stored at the International Bureau of Weights and Measures (known by its French-language initials BIPM) in an environmentally monitored safe in the lower vault located in the basement of the BIPM’s on the outskirts of Paris.
- Three independently controlled keys are required to open the vault. Official copies of the IPK were made available to other nations to serve as their national standards. These are compared to the IPK roughly every 40 years, thereby providing traceability of local measurements back to the IPK.
But is this method reliable? because even under safe and clean conditions these mass have degraded over the years and probably we have something that is nearly 1 kilos but not exactly 1kg.
So, what are the alternatives to these solid element mass? Watch out this space for further information on Mass and weight.
[Information and photo credit: By en:User:Greg L – Originally uploaded to English Wikipedia as CGKilogram.jpg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2547913, Wikipedea]