Quick Facts
Born:
Feb. 15, 1861, Fleurier, Switz.
Died:
June 13, 1938, Sèvres, France (aged 77)
Awards And Honors:
Nobel Prize (1920)
Subjects Of Study:
nickel
ferroalloy

Charles Édouard Guillaume (born Feb. 15, 1861, Fleurier, Switz.—died June 13, 1938, Sèvres, France) was a French physicist whose exhaustive studies of ferronickel alloys culminated in the discovery of invar (a nickel–steel alloy) and gained him the Nobel Prize for Physics in 1920.

In 1883 Guillaume joined the International Bureau of Weights and Measures, Sèvres, and from 1915 served as its director. His early studies there included exhaustive investigations of the mercury thermometer and of the volume of the litre, which he found to be 1,000.028 cubic centimetres, not 1,000.000 cubic centimetres as had been accepted. From 1890 he focused his attention on alloys and developed invar and elinvar. Invar’s low coefficient of expansion (change in volume caused by change in temperature) and elinvar’s low coefficient of elasticity (change in elasticity caused by change in temperature), combined with their low cost, resulted in their widespread use in scientific instruments.

This article was most recently revised and updated by Encyclopaedia Britannica.

International Bureau of Weights and Measures

international organization
Also known as: BIPM, Bureau International des Poids et Mesures
Quick Facts
French:
Bureau International des Poids et Mesures
Date:
January 1876 - present
Areas Of Involvement:
measurement

International Bureau of Weights and Measures (BIPM), international organization founded to bring about the unification of measurement systems, to establish and preserve fundamental international standards and prototypes, to verify national standards, and to determine fundamental physical constants. The bureau was established by a convention signed in Paris on May 20, 1875, effective January 1876. In 1921 a modified convention was signed.

The convention provides for a General Conference that meets every four years to consider required improvements or modifications in standards. An International Committee of Weights and Measures, composed of 18 scientists elected by the conference, meets annually to monitor worldwide uniformity in units of measure. The bureau headquarters at Sèvres, France, serves as a depository for the primary international standards and as a laboratory for certification and comparison of national standard copies.