Isolating elements

These reactions are carried out in the total absence of aqueous solvents, and are used to chemically isolate elements, or groups of elements, from impurities in the feed materials. 

The allowable response of individual frame components is less than that permitted for the same member responding as an isolated element. This is done to reduce the possibility of progressive collapse and to increase redundancy of the frame. Failure of individual girt and purlin components is not as catastrophic as failure of a frame... 

In the mid-1700s a number of scientists experimented with and attempted to isolate element 74 by treating ores of other metals with reagents. One problem was that tungsten was often confused with tin and arsenic. It was not until 1783 that Don Fausto de Elhuyar (1755-1833) and his brother Don Juan Jose de Elhuyar isolated a substance from tin ore that they called wolframite. They named it after the mineral in which it was found. At about the same time the Swedish named it tung sten, which means heavy stone in Swedish. This explains the potentially confusing use of W for the symbol for tungsten. 

Other chemists also worked to separate gadolinium from the mineral dydimia. Paul-Emile Locoq de Boisbaudran, following clues provided by Marignac, isolated element 62 (samarium)... 

When an element is isolated, or separated from every other kind of matter, its atoms still exist, except in a few cases, in combination with each other. In many instances the atoms of isolated elements are associated in pairs when thus combmed. Such an isolated atom or group of atoms constitutes aue/smen-... 

Fig. 8. Schematic of the first gas chromatography apparatus used to chemically isolate element 104 in the form of volatile chlorides (Figure from Ref. 11, adapted from Ref. 105).

Potassium is so active that it never occurs free in nature. It always occurs in compounds, combined with other elements. It was first prepared in pure form in 1807 by English chemist Sir Humphry Davy (1778—1829). Davy used a new method of isolating elements that he had invented called electrolysis. In electrolysis, an electric current is passed through a molten (melted) compound. The electrical current breaks the compound into its elements. 

In the late 1790s, French scientist Antoine, Lavoisier compiled a list of elements known at the time. The list contained 23 elements. Many of these elements, such as silver, gold, carbon, and oxygen, were known since prehistoric times. The 1800s brought many changes to the world, including an explosion in the number of known elements. The advent of electricity, which was used to break compounds down into their component elements, and the development of the spectrometer, which was used to identify the newly isolated elements, played major roles in the advancement of chemistry. So did the industrial revolution... 

Arsenic compounds were known in antiquity, and the name is derived from the Greek arsenikon and the Latin arsenicum. Elemental arsenic may have been discovered by Albertus Magnus in 1250, but this is unclear. In was Johann Schroeder in 1649 who published two methods for producing arsenic, after isolating elemental arsenic. Arsenic was historically used in medicines and was developed as a treatment for syphilis. Its high level of toxicity led to its use as an insecticide. Since arsenic is a semimetallic element, it has properties that make it useful for modern electronics such as transistors. 

The element is named using the Latin name Gallia, for France. It was predicted and described in 1863 by Mendeleev as eka-aluminum and discovered in 1875 by Paul Emile (Francois) Lecoq de Boisbaudran (1838-1912) using spectroscopic analysis. He isolated elemental gallium the same year. The... 

The absolute value enforces that the drag force acts opposite to the direction of fluid motion. Here Cd is the drag coefficient for the array, and it may differ in magnitude from the drag coefficients of isolated elements of the same form (see, e.g., discussions in [88,462, 505]). Note that this definition uses a factor 1/2, which is conventional for hydraulic studies. Many air studies exclude this factor as in equation (4.4) in Chapter 4. Cd is a function of stem Reynolds number, as well as canopy density, a. The dependencies of Cd are discussed below. 

The water cleavage can be easily performed in the laboratory via electrolysis by the use of electrical energy instead of visible light. For the electrolytical water decomposition into its isolated elements two operational units are required a) anelectrical... 

These drops were dried and redissolved. Then Stan forced them through a second column to isolate element 101 from any other elements still present. 

There are three hierarchies. One of them is a trivial hierarchy as it consists of one element only, i.e., element f that is not comparable to any other elements. Such elements are also called isolated elements. If only few isolated elements are found, whereas almost all other are comparable, then the... 

Isolated elements Elements that are both Minimal and Maximal elements. Maximal/Minimal elements which are not isolated, are often called proper maximal/minimal elements. An isolated element in the Hasse diagram, shown in Fig. 12 is f. 

Considering the other clusters of Fig. 6a it is evident that also K2 and K4 consist of samples from almost one river section, namely FL (Fahlberg List) and HM (MciBcn harbour). However, in case of FL cluster K2 is not comparable to the remaining samples of FL four of overall ten samples from FL are assigned to K2. Moreover, most of the samples of FL are incomparable to all other samples (they are isolated elements). Reasons for this specific pattern could be the discontinuous sewage draining from an old contaminated site there. 

In the last case u is an isolated element, i.e. it is not comparable with any of the elements of the training set, thus its rank cannot be predicted by the model ranking developed. 

Fixing on atomic structure does not circumvent this general feature. The electronic structure characteristic of isolated atoms, or of atoms in molecules of the isolated element, is changed in compounds. Preservation of nuclear structure, even if necessary, is clearly not sufficient to explain the presence of elements whose chemical features are supposed to specifically depend on electronic properties. The fact that considerations of this kind led Paneth (1962) to question whether modern... 

Ksenzenko, V.I., Khojamamedov, A.M., Kuliev, Ch.A., and Ovezova, O., The behaviour of rare and isolated elements during the isothermic evaporation of underground mineralized waters at the Gaurdak deposit , Izvestia AS TSSR, Series of Physical-technical chemical and geological sciences, 1978, (3), 104-107. 

The properties of arsenic sulfides were known to physicians and professional poisoners in the fifth century B.C.E. Albertus Magnus (1193-1280) is credited with having isolated elemental arsenic by heating auripigment (AS2S3) with soap. 

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