English in Analytical Chemistry communicating about Methods & Techniques. Учебное пособие. Книга для студента

amount of air or water is simply filtered to collect the solid matter. An analyte in solution is removed from solution by precipitation with a suitable reagent. For an analyte that is present as a component of a solid, the solid must be dissolved to perform the precipitation. The precipitate is collected by filtering, rinsed to remove impurities, and dried. If necessary a high temperature ignition converts the precipitate to a pure form. Ignition involves heating to a high temperature with a flame or a muffle furnace (a high temperature oven). All steps in a gravimetric procedure have the goal of achieving quantitative collection and conversion to a pure substance. When this requirement is met, the mass of the weighed substance can be related back to the number of moles of analyte in the original sample. As the following example illustrates, a real gravimetric laboratory procedure will have many more steps than are listed in the outline in Table 1. Each individual step ensures that the overall process is quantitative with a pure final product. Handbooks and procedures will list “gravimetric factors” for specific gravimetric methods. These factors include the formula weights of the precipitate and analyte so that multiplying a precipitate weight by the gravimetric factor gives the analyte weight.