Present Status of Precise Information on the Universal Physical Constants. Has the Time Arrived for Their Adoption to Replace Our Present Arbitrary Conventional Standards?

Three years ago Dr. E. R. Cohen and I prepared and published our latest (1955) least-squares adjustment of all the most reliable data then available bearing on the universal constants of physics and chemistry. Since then new data and information have been accumulating so that a year or two from now the time may perhaps be propitious for us to prepare a new adjustment taking the newly-gained knowledge into account. At present it is too early to attempt such a re-evaluation since many of the investigations and re-determinations now under way are still far from completed. I shall be obliged, therefore, to content myself in this talk with a description of the sources of information upon which our 1955 evaluation was based, mentioning however, the weak points where these are now either well established as errors or at least considered to be under strong suspicion of systematic error. I shall also tell you a little of some of the new re-evaluations now under way

Journey of Kilogram from Physical Constant to Universal Physical Constant (h) via Artefact: A Brief Review

The redefinition of mass adopted in November 2018 and implemented from 20 May 2019, i.e. World Metrology Day, eliminated the artefact-based approach dependent upon the International Prototype of the Kilogram (IPK), in favour of realizing the kilogram in terms of the Planck constanthby fixing its value as 6.62607015 x 10(-34) J s. In this paper, the authors present a general outline of the circumstances and related developments that paved the way for the new definition that replaced the IPK after a period of 130 years since it was formally sanctioned to define the kilogram in 1889. The new definition opens up fascinating developments in mass metrology which include different realization techniques, realizing the unit at values other than 1 kg, numerous sources for traceability can be envisaged etc

A critical review of the proposed definitions of fundamental chemical quantities and their impact on chemical communities (IUPAC Technical Report)

In the proposed new SI, the kilogram will be redefined in terms of the Planck constant and the mole will be redefined in terms of the Avogadro constant. These redefinitions will have some consequences for measurements in chemistry. The goal of the Mole Project (IUPAC Project Number 2013-048-1-100) was to compile published work related to the definition of the quantity \u2018amount of substance\u2019, its unit the \u2018mole\u2019, and the consequence of these definitions on the unit of the quantity mass, the kilogram. The published work has been reviewed critically with the aim of assembling all possible aspects in order to enable IUPAC to judge the adequateness of the existing definitions or new proposals. Compilation and critical review relies on the broadest spectrum of interested IUPAC members.Peer reviewed: YesNRC publication: Ye

The precision measurement of mass

A method has been described for obtaining the density of air quickly without resort to measurement of the prevailing atmospheric conditions and with accuracy sufficient to enable the correction for the buoyancy of air on a weighing to be made to better than one part per million. The method involves the weighing in air in quick succession of two objects, a hollow cylinder of stainless steel (density 0.5 g./cm.(\u273)) and a solid counterweight of equal mass and area in the form of a stainless steel tube (density 8.11 g./cm.(\u273)). The densities of these objects have been obtained from the volume as determined by high-precision hydrostatic weighing and by measurements of the dimensions and from the mass as determined by weighing in an actual vacuum ( vacuum weighing bottle ). The density of air obtained by weighing this absolute density cylinder and counterweight has been compared to the density calculated from measurements of the atmosphere, made at the same time in a constant temperature room ((+OR-)0.075(DEGREES)) and with high-precision instruments, of the barometric pressure and temperature and gravimetric determination of water and carbon dioxide contents. The density of air determined by the cylinder was 3.4 parts per thousand greater than that calculated from the prevailing conditions. Possible explanations for the discrepancy have been examined with particular reference to the oxygen content of the atmosphere; the discrepancy is left unexplained but it is recommended that for the high-precision measurement of mass that the density of air be measured with a cylinder such as the one described;A method has been proposed for the high-precision determination of the oxygen content of the atmosphere;Modifications of the Mettler single-pan balances have been described to increase capacity and sensitivity and eliminate electrostatic effects;It has been proposed to replace the International Kilogram with a kilogram mass of a corrosion-resistant stainless steel the surface of which has been rendered nonpolar by chemical treatment and to subdivide the kilogram in an actual vacuum using a set of weights constructed on the basis of the Fibonacci sequence. Fabrication of such a set of weights has been started. A mathematical theory has been developed for the calibration of this set in which advantage is taken of the numerous possible cross checks on the experimental work afforded by the characteristics of the Fibonacci numbers

Studies in the System H2SO4-H2S2O7: Part I. Vapour Pressure of Fuming Sulphuric Acid. Part II. Dielectric Dispersion of Sulphuric Acid

Abstract Not Provided

Theory and applications of atomic and ionic polarizabilities

Atomic polarization phenomena impinge upon a number of areas and processes in physics. The dielectric constant and refractive index of any gas are examples of macroscopic properties that are largely determined by the dipole polarizability. When it comes to microscopic phenomena, the existence of alkaline-earth anions and the recently discovered ability of positrons to bind to many atoms are predominantly due to the polarization interaction. An imperfect knowledge of atomic polarizabilities is presently looming as the largest source of uncertainty in the new generation of optical frequency standards. Accurate polarizabilities for the group I and II atoms and ions of the periodic table have recently become available by a variety of techniques. These include refined many-body perturbation theory and coupled-cluster calculations sometimes combined with precise experimental data for selected transitions, microwave spectroscopy of Rydberg atoms and ions, refractive index measurements in microwave cavities, ab initio calculations of atomic structures using explicitly correlated wave functions, interferometry with atom beams, and velocity changes of laser cooled atoms induced by an electric field. This review examines existing theoretical methods of determining atomic and ionic polarizabilities, and discusses their relevance to various applications with particular emphasis on cold-atom physics and the metrology of atomic frequency standards.Comment: Review paper, 44 page