Atomic Weights Of Elements Research Articles

Thin film standardless analysis used in TEM asbestos EDS analysis

A thin film standardless analysis method, based on the Cliff-Loriner factor k, has been used to do quantitative x-ray analysis of asbestos fibers in the TEM. The results of the analysis of four minerals at 120 keV were close to the theoretical value. The ionization cross section Q has been revised experimentally to improve the analysis of asbestos.The Cliff-Lorimer factor has been used in TEM thin film analysis since 1975. The factor kAB is used in the following equation:CA/CB= kABIA/IBwhere CA and CB is the weight percent of the elements A and B. The IA and IB are x-ray intensities corresponding to elements A and B. In this paper the calculated k values2 will be used for standardless quantitative analysis.In the thin film, when the effects of the backscattering electron, x-ray absorption, and secondary fluorescence are not considered, the x-ray intensity iswhere pt is the mass depth AA is the atomic weight of element A, W is the fluorescence yield, L is the ratio of the x-ray lines and T is the detector efficiency.

Atomic Weights of Elements

Atomic Weights of Elements

New Scale of Nuclidic Masses and Atomic Weights

A discussion is presented of the situation which led to the existence of the chemicai scale (atomic weight of element O = l6) and the physical scale (atomic weight of principal O isotope = 16) and of the considerations that led to their replacement by a new scale. ln 1959, the lnternatlonal Commission of Atomlc Weights recommended the adoption of C12 as the reference species wlth assigned relative mass of 12, since this isotope was acceptable to both chemists and physicists. The lnternational Union of Pure and Applied Physlcs and the International Unlon of Pure and Applled Chemlstry adopted this recommended scale. A table of atomic weights developed from a complete review of experimental data on the basis of the new scale ls presented together wlth a separate table for radloactive elements. (D.L.C.)

Шкала атомных весов <sup>12</sup>C = 12 и новые таблицы атомных весов элементов и масс нуклидов

Шкала атомных весов <sup>12</sup>C = 12 и новые таблицы атомных весов элементов и масс нуклидов

Early History of Mendeléeff's Periodic Law

THE statement appears in NATURE of April 28, p. 656, that “Mendeleeff's first table, published in 1871, bears a remarkable resemblance to that of the present day”. As a matter of fact, Dmitri Ivanovitch Mendeleeff began his investigations on the correlation of chemical properties with the atomic weight of elements in 1868, and succeeded in evolving the periodicity of this relationship at the end of that year. He printed the first periodic table in the middle of February, 1869, as follows:

The Atomic Weight of Silver

IN NATURE of Dec. 11, 1926, reference is made to the determination of the atomic weight of silver (Trans. Chem. Soc., 1926, p. 2510) by H. Brereton Baker and H. L. Riley, who, by determining directly the ratio Ag: O in pure silver oxide have obtained the value 107.864 ± 0.0013. This work, carried out with the greatest ingenuity and with care and exactitude such as has only been reached by Th. W. Richards and his school, is of cardinal importance. As I have the honour to be chairman of the Sub-Committee for Atomic Weights of the International Commission on Chemical Elements, I have perhaps the right, as well as the official duty, of offering a few critical remarks. I may be allowed to add that I have studied the literature of atomic weights for fifty years and I was the first to propose, in 1888, the adoption of O = 16 as the standard of atomic weights. A like proposal was made almost simultaneously by Venable in America, and, as is well known, this has become the established practice. As the atomic weights of elements cannot as a rule be determined directly in relation to oxygen, secondary standards are required, and the most modern work published by Richards and his school is being carried out by finding the ratios xAg: RClx or yAg: RBry, to determine the atomic weight of R.

The Standard of Atomic Weights

IT is with considerable surprise, as a chemist, that I see in NATURE of April 22, p. 230, arguments as to the structure of atoms based on the deviations of the atomic weights of elements from whole numbers on the standard O = 16.00 The reasons for the use of this arbitrary and inconvenient standard are now matters of ancient history, and the values of Stas, which were regarded as fundamental at the time when the standard was adopted, have now been shown by many independent lines of experiment to be inexact. It is almost pathetic to observe modern experimenters who have determined equivalents by the accurate analysis of hydrogen compounds, such as hydrogen chloride, methane, hydrogen bromide, ammonia, etc., all of which are more easily obtained in a state of purity, and analysed, than oxygen compounds, compelled to multiply their results by 1.008 in order to bring them into line with the standard of O = 16.00.

Atomic weights of elements

"Atomic weights of elements." The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 21(139), p. 409