This Dictionary of Chemistry presents a clear convenient and immediately accessible reference book. Every aspect of its conception and layout has been planned to help the user to find the scientific information he needs with minimum difficulty and numerous branches of engineering and technology that are concerned with the functioning of nature: living organisms and their ecological relationships processes and cycles in atmosphere hydro- sphere and lithosphere; hazards resulting from pollution including the description of noxious substances working all the time on ourselves and our environment; and the disposal or recycling of the waste products. Restraint must prevail particularly in a Dictionary such as this of modest proportions. The terms included have been selected in a somewhat pragmatic manner partly on the basis of those most frequently encountered by the authors within the context of general usefulness of the subject. This Dictionary is expected to be a good source book not only for the students and teachers but it will prove to be quite useful for persons working in the chemical industry and those who intend to setup new industry.