Upper spoils

The red string is used as a mark for the next assembly. Remove the upper mould and then the bottom mould. Wind white cotton string around the sphere taking care not to spoil the shape(6). In this way the centre sphere is... 

Mines produce tremendous quantities of waste rock and tailings which have to be disposed of on land or into aquatic ecosystems. The increase of waste material is depending on the type of exploitation, the quality of raw material output as well as on the efficiency of beneficiation. It is estimated that in Poland during the years 1984-2000 about 900 million cubic metres of spoils will be dumped only in the area of the Upper Silesian Coal Basin. The annual load of chlorides in these spoils reaches 40 (X)0 tons. 

Most heavy metals as well acids in mining areas originate from the weathering of sulphides (e.g. FeS2, PbS, ZnS) contained in spoils (e.g. in the Upper Silesian Coal Basin under full oxygenation, the decomposition of sulphides may yield per year 450 000 tons of sulphates). Many dumps may produce acid mine water with a pH below 4. 

The area of chemistry that is concerned with the speeds, or rates, of reactions is called chemical kinetics. Chemical kinetics is a subject of broad importance. It relates, for example, to how quickly a medicine is able to work, to whether the formation and depletion of ozone in the upper atmosphere are in balance, and to industrial problems such as the development of catalysts to synthesize new materials. Our goal in this chapter is not only to rmderstand how to determine the rates at which reactions occur, but also to consider the factors that control these rates. For example, what factors determine how rapidly food spoils How does one design a fast-setting material for dental fillings What determines the rate at which steel rusts What controls the rate at which fuel bums in an automobile engine Although we won t address these specific questions directly, we will see that the rates of all chemical reactions are subject to the same basic principles. 

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