물질의 양에 대한 SI 기본단위 몰과 아보가드로 상수를 이용한 재정의

Abstract

The mole, symbol mol, is the International System of Units (SI) unit of the amount of substance which is the quantity referring to a measure of the number of specified elementary entities, such as chemical elements or compounds in a sample. In the current SI, the mole is defined by specifying the mass of carbon-12. But this base unit is not an invariant of nature because the mass is defined by the material artefact. According to efforts to define the base units in SI using true invariants of nature, the mole will be redefined by fixing the numerical value of a fundamental constant, the Avogadro constant. In the new SI, the definition of the mole can be realized through the experiments that lead to the determination of the Avogadro constant. The best experimental value of the Avogadro constant has been obtained by the X-ray crystal density experiment using silicon-28 highly enriched silicon sphere in the frame work of the International Avogadro Coordination. In this paper, the current definition of the mole and practical aspects of this unit are introduced, then the principle and technical challenges in X-ray crystal density experiment for redefinition of the mole are discussed.