= Charles-Édouard Guillaume
{c}
{tag=Physicist}
{title2=1861–1938}
<Charles-Édouard Guillaume> investigated iron-nickel alloys whose thermal changes are unusually small. <Invar> has low thermal expansion over a useful <temperature> range, making it valuable for dimensional references. <Elinvar> addresses a related metrological problem through a small <temperature> dependence of elasticity, useful when an instrument's behavior depends on an elastic element. These materials show why composition and magnetic behavior can matter as much as geometrical precision when building a stable measuring instrument.<Nobel Lectures, Physics 1901–1921/Invar and Elinvar by Charles-Édouard Guillaume>[Nobel lecture, alloy properties and precision-instrument applications]{ref}
A <physicist>.https://library.ethz.ch/en/collections-and-archives/short-portraits/guillaume-charles-edouard-1861-1938.html[Independent professional biography and identity]{ref}
\Image[https://upload.wikimedia.org/wikipedia/commons/6/62/Charles_Edouard_Guillaume.jpg]
{title=Portrait of <Charles-Édouard Guillaume>}
{width=240}
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