Chemical hazards with solvents

Begun in 1944 with DDT and in 1947 with parathion, the present report includes analytical data secured from certain chemical, mechanical, and solvent actions on apples, pears, lemons, and oranges. In the absence of established tolerances for these two insecticidal materials, it is hardly possible to interpret the significance of many of these data with respect to consumer hazard. 

In the 21st century, the chemical industry will be increasingly influenced by environmental concerns with respect to waste treatment. Consequently, one of the aims of green chemistry is the replacement of hazardous materials (solvents, reagents) by less hazardous substances [1-3]. In order to comply with the requirements of a sustainable development, modern state-of-the-art chemistry should comprise ... 

With knowledge of how to manipulate and transform chemicals, coupled with the basic hazard data that can be accessed readily from a variety of sources, chemists have the power to reduce or eliminate the risk posed to themselves and society in general by the chemical enterprise (Anastas and Warner, 1998). Specifically in the areas of solvent use, this text will provide leading articles and examples of its practice. Researchers at the vanguard of innovation in this new area know that these goals can be accomplished. 

This book was written to provide readers with some knowledge of electrochemistry in non-aqueous solutions, from its fundamentals to the latest developments, including the current situation concerning hazardous solvents. The book is divided into two parts. Part I (Chapters 1 to 4) contains a discussion of solvent properties and then deals with solvent effects on chemical processes such as ion solvation, ion complexation, electrolyte dissociation, acid-base reactions and redox reactions. Such solvent effects are of fundamental importance in understanding chem-... 

Chemical procedures that produce less waste or less hazardous waste are said to be green because they reduce harmful environmental effects. In chemical analyses with dithizone, you can substitute aqueous micelles (Box 26-1) for the organic phase (which has traditionally been chloroform, CHC13) to eliminate chlorinated solvent and the tedious extraction.2 For example, a solution containing 5.0 wt% of the micelle-forming surfactant Triton X-100 dissolves 8.3 X 10 5M dithizone at 25°C and pH < 7. The concentration of dithizone inside the micelles, which constitute a small fraction of the volume of solution, is much greater than 8.3 X 10 5M. Aqueous micellar solutions of dithizone can be used for the spectrophotometric analysis of metals such as Zn(II), Cd(Il), Hg(Il), Cu(ll), and Pb(II) with results comparable to those obtained with an organic solvent. 

The ability to rapidly assess or monitor the disposition of environmental contaminants at purported or existing hazardous waste sites is an essential component of green chemistry. Soil samples, which represent approximately half the total number, are extracted with solvents, and then further separated using additional solvent to produce chemical-specific fractions. Each fraction is then analyzed using an appropriate method. The new technology proposed at the Tufts... 

Solvents. Solvents commonly used in epoxy resin applications present a flammability hazard. These solvents present other special health hazards. Contact with solvents will cause defatting and drying of the skin, which enhances the chance for skin irritation. Some solvents are absorbed directly though the skin, and absorption may be enhanced if the skin is abraded or irritated. They also have the ability to dissolve other epoxy resin system chemicals and carry them through the skin. The inhalation of solvent vapors or mists may cause respirator irritation and depression of the central nervous system. 

The welfare of the people who work with chemical products and processes is at least as important as the welfare of the environment. Green chemistry is anthropocentric (as is sustainable development). Several green chemistry principles reflect this anthropocentrism. Principles 3 (less-hazardous chemical synthesis), 4 (design of safer chemicals), 5 (safer solvents and auxiliaries), and 12 (inherently safer chemistry for accident prevention) express concern for the health of the people who handle materials or attend to processes (Anastas and Warner, 1998). While many of these safety benefits also accrue to nonhuman organisms, the focus of the principles is on the people who are exposed to these materials and methods. Inasmuch as we cannot know all of the environmental needs of nonhuman things, it is hard to imagine how the focus could be on anything else. 

Solvented silicone systems may be hazardous with regard to health or fire. Further, primers are flammable and require care in handling. Methylchlorosilanes are flammable and corrosive because of the liberation of hydrochloric acid on hydrolysis other chlorosilanes are less flammable but are hazardous chemicals and can irritate the eyes, respiratory organs and skin. Protective gloves should be used. The material should not be allowed to make contact with the eyes or skin. Inhalation of vapours should be avoided especially in systems which evolve irritant by-products such as acetic acid or amines. 

Safety. Solvents with low potential for fire and reactive chemistry hazards are preferred as inherently safe solvents. In all cases, solvents must be used with a full awareness of potential hazards and in a manner consistent with measures needed to avoid hazards. For information on the safe use of solvents and their potential hazards, see Sec. 23, Safety and Handling of Hazardous Materials. Also see Growl and Louvar, Chemical Process Safety Fundamentals with Applications (Prentice-Hall, 2001) Yaws, Handbook of Chemical Compound Data for Process Safety (Elsevier, 1997) Lees, Lo.ss Prevention in the Process Industries (Butterworth, 1996) and Bretherick s Handbook of Reactive Chemical Hazards, 6th ed., Urben and Pitt, eds. (Butter-worth-Heinemann, 1999). 

The elimination of solvents in chemical processes, or the replacement of hazardous solvents with environmentally benign ones, is one of the Twelve Principles of Green Chemistry [13]. The main advantage of solventless chemistry is that it is conceptually the simplest solution for the problems with solvents. However, not many reactions can be carried out under such conditions, as exothermic reactions can be dangerous, heating and stirring can be inefficient, especially if solid reactants or products are present, and usually solvents are needed for working up the product from solventless reaction media. 

By the late 1970s evidence had accumulated on the potential hazards of certain extraction solvents, especially chlorinated hydrocarbons. Increased scrutiny of traditional industrial solvents is responsible for spawning another large body of R D programs on SCF processes. Increased consumer awareness of potential chemical hazards coupled with the uncertainty of future governmental regulatory action motivated an examination of supercritical fluids as extraction solvents for foods, beverages, and spices. 

The discussion to be provided here will be limited to an outline of the general principles involved and certain precautions that must be observed. One important precaution involves fire and explosion hazards. Many solvent vapors, when mixed with air in certain proportions, are explosive, the degree of explosiveness depending upon the proportion of vapor to air. No explosion will occur when the vapor concentration is below a critical amount which varies from 0.5-10% according to the chemical nature of the vapor. As the vapor concentration increases above this lower critical point, the... 

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