Amount of substance

News

Better Flowmeters with the Big Blue Ball

February 24, 2017

Last year, upwards of 25 trillion cubic feet of natural gas were delivered to customers in the United States, and when...

How Sweet It Is: NIST Metrology and the Maple Syrup Industry

January 04, 2017

NIST is frequently asked to provide unusual, sometimes downright exotic, measurements and calibrations in support of U...

Redefining the SI Base Units

November 02, 2011

Note: Much more recent information is available about redefinition of the SI units. For a comprehensive general...

'Sí' on the New SI: NIST Backs Proposal for a Revamped System of Measurement Units

October 26, 2010

Taking the first steps of what would be a major historical advance in the science of measurement, the National...

Publications

An improved result on the measurement of the Avogadro constant from a 28Si crystal

March 25, 2015

Author(s):

Yasushi Azuma, G Barat, Guido Bartl, Horst Bettin, Michael Borys, I Busch, L Cibik, G D' Agostino, K Fujii, H Fujimoto, A Hioki, Michael Krumrey, U Kuetgens, N Kuramoto, Giovanni Mana, E Massa, R Meess, Shigeki Mizushima, T Narukawa, Arnold Nicolaus, Axel Pramann, Savelas A. Rabb, Olaf Rienitz, C Sasso, M Stock, Robert D. Vocke Jr., A Waseda, S Zakel

In this paper new results of an international research project aimed at determining the Avogadro constant by counting the atoms in an isotopically enriched...

Absolute Silicon Mass Measurements in support of the International Avogadro Project and the Redefinition of the Kilogram

June 25, 2014

Author(s):

Robert D. Vocke Jr., Savelas A. Rabb, Gregory C. Turk

As the Planck and Avogadro constants are tied by the molar Planck constant, any redefinition of the kilogram using an accurately determined Planck constant (h...

High-Accuracy Measurements of the Vapor Pressure of Ice Referenced to the Triple Point

December 06, 2013

Author(s):

Katarzyna E. Bielska, Daniel K. Havey, Gregory E. Scace, D Lisak, Allan H. Harvey, Joseph T. Hodges

The vapor pressure of hexagonal (Ih) ice was measured over the temperature range 175 K to 253.4 K and referenced to the value at the triple point of water...

A Humidity Generator for Temperatures to 200 °C and Pressures to 1.6 MPa

November 30, 2012

Author(s):

D Vega-Maza, W Wyatt Miller, Dean C. Ripple, Gregory E. Scace

We have constructed a new humidity generator that produces gas streams of known moisture content at temperatures from 85 °C to 200 °C, absolute...

Projects & Programs

Advanced Ambient Mass Spectrometry, Secondary Ion Mass Spectrometry and Ion Mobility Spectrometry

International Comparisons for Chemical Measurements

Because of NIST's role as the National Metrology Institute (NMI) in the U.S., the Chemical Sciences Division's measurement capabilities must be benchmarked...