Systematic analysis on the semimicro scale. General considerations

3 SYSTEMATIC ANALYSIS ON THE SEMIMICRO SCALE. GENERAL CONSIDERATIONS The object of systematic qualitative analysis on the semimicro scale is not only to detect the constituents of a given mixture, an equally important aim is to ascertain the approximate relative amounts of each component. For this purpose about 0-2 g of material is usually employed for the analysis the relative magnitudes of the various precipitates will provide a rough guide as to the proportions of the constituents present. Systematic semimicro analysis is carried out in the following steps  

The preliminary examination of the solid sample This includes preliminary examination by dry tests, examination of the volatile products with sodium hydroxide solution (for ammonium), and with dilute and concentrated sulphuric 

Testing for anions in solution This includes the preparation of a soda extract , followed by systematic tests. These, in turn, can be made conclusive by confirmatory tests. 

Testing for cations in solution The sample must be dissolved first, then subjected to preliminary tests and separations. Finally, the presence of each cation must be confirmed by suitable reactions. 

Note that the order here is reversed, i.e. anions are tested for first, followed by tests for cations. Experience has shown that once the preliminary tests are carried out, considerable information is collected about the presence or absence of certain anions, and it is worthwhile to carry on with anion testing at this stage, always keeping in mind the results obtained by the preliminary tests. The systematic analysis for cations follows this, based again on the separation of each single cation as in macro analysis, and on specific tests carried out after the separation of the cations. 

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