History and Chemical Background

Earlier searches starting with elemental gallium having been to no avail, the first substantive claim to the synthesis of gallium hydride 

Doubts about the authenticity of some of these claims were raised about 20 years later by the failure of attempts to reproduce the experiments (31,32). On the other hand, analytical and spectroscopic evidence was presented (32,33) to support the low-temperature displacement reaction 

All these vicissitudes must, we feel, call in question the preparation of anything approaching pure gallane in the period before 1989. Mono-substituted derivatives of gallane, [H2GaX] , have been no less elusive. The displacement reaction 

The chloride forms white crystals that melt at 29°C with decomposition and, when heated to 150°C, decompose quantitatively into gallium dichloride, Ga[GaCl4], and hydrogen. Several diorganogallanes were also described. Among these were [Et2GaH] (43-45) and [Bu 2GaH] (46) prepared, for example, by reactions such as (7) and (8)  

Only recently, however, with the isolation and more detailed interrogation of the compounds [Me2GaH] (47) and HGa(BH4)2 (48-50), has it been possible to discover with any sureness the properties—including the structures—of such compounds. Insofar as these properties have a bearing on the hunting of other gallium hydrides, it will be better that we elaborate on them in due course (in Section IV). 

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The chemistry of jS-carbolines of plant origin (5b-f) as well as the history and ethnopharmacological background of these alkaloids have been reviewed (5d). The chemistry of the mammalian j3-carbolines relevant to synthesis and further chemical transformation, however, has never been presented. With the information detailed in Figs. 4-7, and in Fig. 8 for the preparation of optically active representatives, this gap has now been filled. 

In this introductory chapter, a broad overview is given of the history of chemical warfare on earth, and the compounds, species, and mechanisms involved. The impact of human-made compounds on the environment, which is the subject of this book, is an extremely recent event in evolutionary terms. It is important to take a holistic view, and to see the effects of human-made pollutants on the environment against the background of chemical warfare in nature. 

I cite this history including these two recent examples of attempts to insert chemistry into the thicket of materials research already densely populated by physicists, ceramists, metallurgists, and chemical and civil engineers, because they form the background for my recommendations in the following sections. It is, of course, directly relevant to the initiative in education of the American Chemical Society. First let me list good reasons for such an initiative ... 

We shall begin with a little history, and then move to a discussion of cancer statistics and the causes of cancer, and then provide some background on cancer biology and the mechanisms of tumor development. Some of the general characteristics of chemical carcinogens will also be covered. The methods for identifying chemical carcinogens are the subject of Chapter 6. How their risks are estimated is left to later chapters. 

Contaminant distribution in soil and water depends on such factors as soil properties the physical and chemical properties of the contaminant contaminant fate and transport in soil, groundwater or surface water and even the manner in which the contaminant was introduced into the environment. The knowledge of these issues coupled with available information on site history and background allows us to make valid assumptions in the planning phase on contaminant distribution and variability at the site. 

History and Background Information Lewisite (also known as Agent L) is no longer considered a state-of-the-art chemical warfare agent (Franke, 1967 Goldman and Dacre, 1989). Lewisite is relatively simple and inexpensive to produce (Franke, 1967). 

The IDE submission is the cmcial hurdle and major milestone that transitions a promising material into a viable and testworthy medical device. The IDE s format is a testament to this transformation. The first half of the submission is a detailed report of the injectable biomaterial s evolution and optimization -including all background data and all reports of prior investigation. This section includes the history of the material, all current mechanical and chemical testing, in vitro and in vivo modeling, and biocompatibility results. The second half of the submission, however, focuses on the injectable biomaterial as a device. This... 

The examinations are to include a medical history and work history, and are to emphasize symptoms associated with exposure to hazardous chemicals, and health hazards and the employee s fitness for duties requiring the wearing of PPE under conditions that might be expected during the employee s work assignments. The examinations are to be done by or under the supervision of a licensed physician, preferably one with a background in occupational medicine. 

This early history of the hydrolysis of starch is the chemical background against which the technical study of catalysis and enzymology began. 

Elizabeth K. Weisburger. History and background of the Threshold Limit Value Committee of the American Conference of Governmental Industrial Hygienists. Journal of Chemical Health and Safety 8(4) 10-12 (2001). 

The story of Lavoisier s discovery of oj gen is a stock feature of virtually all surveys of the history of chemistry. For a recent example, see Robert Siegfried, From Elements to Atoms A History of Chemical Composition (Philadelphia American Philosophical Society, 2002), pp. 163-182. For additional background to Lavoisier s famous discoveries, see Henry Guerlac, Lavoisier The Crucial Year The Background and Origin of His First Experiments on Combustion in 1772 (New York Gordon and Breach, 1961) Frederic Lawrence Holmes, Antoine Lavoisier— The Next Crucial Year Orthe Sources of His Quantitative Method in Chemistry (Princeton Princeton University Press, 1998) and Louise Palmer, The Early Scientific Work of Antoine Laurent Lavoisier In the Field and in the Laboratory, 1763-1767 (Ph.D. diss., Yale University, 1998). 

Only against this background can we turn to living cells to examine them as systems. We shall presume that the steps in understanding any chemical system, living or dead, have to be the same, and with the above history of chemistry behind us and the future of biology in front of us, we can state them clearly as follows ... 

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