Biologia e química
Selected Methods of Analysis
Chemistry is primarily an experimental science. This chapter presents a variety of laboratory experiments, from classical titrations and gravimetry to instrumental methods such as chromatography and spectroscopy. Detailed directions are given for each experiment.
his chapter contains detailed directions for performing a variety of chemical analyses. The methods have been chosen to introduce you to analytical techniques that are widely used by chemists. For most of these analyses, the composition of the samples is known to the instructor. Thus, you will be able to judge how well you are mastering these techniques. Your chances of success in the laboratory will greatly improve if you take time before you enter the laboratory to read carefully and understand each step in the method and to develop a plan for how and when you will perform each step. The discussion in this section is aimed at helping you develop efficient work habits in the laboratory and also at providing you with some general information about an analytical chemistry laboratory. Before you start an analysis, you should understand the significance of each step in the procedure to avoid the pitfalls and potential sources of error that are inherent in all analytical methods. Information about these steps can usually be found in (1) preliminary discussion sections, (2) earlier chapters that are referred to in the discussion section, and (3) the “Notes” that follow many of the procedures. If, after reading these materials, you still do not understand the reason for doing one or more of the steps in the method, consult your instructor before you begin laboratory work. The Accuracy of Measurements In looking over an analytical procedure, you should decide which measurements must be made with maximum precision, and thus with maximum care, as opposed to those that can be carried out rapidly with little concern for precision. Generally,