Qualitative analysis of metal ions

In the qualitative analysis scheme for metal ions, a cation is usually detected by the presence of a characteristic precipitate. For example, silver ion gives a white precipitate with chloride ion. But other ions also give a white precipitate with chloride ion. Therefore, you must first subject a mixture to a procedure that separates individual ions before applying a precipitation test to any particular ion. 

Flowchart of the qualitative analysis scheme for the separation of metal ions 

The first group of ions consists of those precipitated by HCI. The separation of the next two groups is based on the differences in solubilities of the metal sulfides.The fourth group consists of ions of the alkaline earth elements, which are precipitated as carbonates or phosphates.The final group of ions is in the filtrate after these precipitations. 

The solubility of the metal sulfides at different pH was discussed in Section 18.4. 

Hydrogen sulfide is often prepared in the solution by adding thioacetamide, CH3CSNH2, and warming. 

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The flame of an alcohol lamp looks almost colourless. Vhen a length of platinum v/ire which is dipped into a metal salt solutioh is put into the flame, the flame is coloured in the upper part by the wire. The colour is peculiar to the kind of the metal strontium colours the flame red, sodium yellow, barium pale green and copper blue. This is applied to the qualitative analysis of metal ions as the colour flame test. The emission of the coloured light is caused by atomic metal gas or a gas consisting of molecules of metal compound, and the process may be set out as follows ... 

For some applications, the qualitative analysis of metal ions is desired detecting and distinguishing which metal ions might be present in a mixture. For other applications,... 

Reagent papers are made use of in the qualitative analysis of metal ions. Frequently it is necessary to know the be-... 

SECTION 17.7 Metallic elements vary a great deal in the solubilities of their salts, in their acid-base behavior, and in their tendencies to form complex ions. These differences can be used to separate and detect the presence of metal ions in mixtures. Qualitative analysis determines the presence or absence of species in a sample, whereas quantitative analysis determines how much of each species is present. The qualitative analysis of metal ions in solution can be carried out by separating the ions into groups on the basis of precipitation reactions and then analyzing each group for individual metal ions. 

Separation of Ions Using Differences in Solubility Fractional Precipitation Qualitative Analysis of Metal Ions in Solution... 

Hydrogen sulfide used to have importance in analytical chemistry for well over a century, in the qualitative inorganic analysis of metal ions. In these analyses, heavy metal (and nonmetal) ions (e g., Pb(II), Cu(II), Hg(II), As(III)) are precipitated from solution upon exposure to H2S. The components of the resulting precipitate redissolve with some selectivity. 

Detailed procedures for separating and identifying all the ions can be found in general chemistry laboratory manuals. Although modern methods of metal-ion analysis employ sophisticated analytical instruments, qualitative analysis is still included in many general chemistry laboratory courses because it is an excellent vehicle for developing laboratory skills and for learning about acid-base, solubility, and complex-ion equilibria. 

The Qualitative Analysis activity in eChapter 16.15 shows the procedure for separating a mixture of metal ions into groups that may be further analyzed to determine the specific ions present. 

Precipitation of sulphides Hydrogen sulphide gas is a frequently used reagent in qualitative inorganic analysis. When hydrogen sulphide gas is passed into a solution, metal sulphides are precipitated. For this precipitation the rule mentioned above can be applied precipitation may take place only if the product of concentrations of metal ions and sulphide ions (taken at proper powers) exceed the value of the solubility product. While the concentration of metal ions usually does fall into the range of 1-10 3 mol 1, the concentration of sulphide ion may vary considerably, and can easily be selected by the adjustment of the pH of the solution to a suitable value. 

Give two examples of metal ions in each group (1 through 5) in the qualitative analysis scheme. 

The rapid development of mass spectrometric technology and the wide field of applications exclude a complete and comprehensive discussion of mass spectrometric possibilities for trace analysis of metals. Therefore, this report will give a brief outline of the principles of mass spectrometry (MS) and the fundamentals of qualitative and quantitative mass spectrometric analysis with emphasis on recent developments and results. The classical methods of analysis of solids, i.e. spark-source MS and thermal ionization MS, as well as newer methods of metal analysis are described. Focal points in this survey of recently developed techniques include secondary ion MS , laser probe MS , plasma ion source MS gas discharge MS and field desorption MS . Here, a more detailed description is given and the merits of these emerging methods are discussed more explicitly. In particular, the results of the FD techniques in elemental analyses are reviewed and critically evaluated. 

The lattice defect of Ce02 is always an issue in the field of cosmetic application for UV shield materials. In order to reduce the photo catalytic activity, a small amount of metal ions are doped to keep the stoichiometry. Similarly this doping method is taken in the sintering process of CeOa to control the grain growth [21, 22]. In such cases, qualitatively, computational analysis gives an interpretation for the mechanism of functional properties. Table 4-8 shows pseudo potential used for ab-initio band stmcture calculation and Figure 4-10 shows the results of band stmcture... 

Another step in the qualitative analysis of cations (see Exercise 28) involves precipitating some of the metal ions as the insoluble sulfides (followed by subsequent treatment of the mixed sulfide precipitate to separate the individual ions). Write balanced net ionic equations for the reactions of Co(ll), Co(lll), Fe(ll), and Fe(lll) ions with sulfide ion,... 

QUALITATIVE ANALYSIS FOR METALLIC ELEMENTS We explain how the principles of solubility and complexation eqiilibria can be used to identify ions in solution. 

The present account brings together the themes which led to that first resolution of a purely inorganic compound, defined as containing no carbon of any kind. These themes are first, optic activity and its relation to stereochemistry second, an aspect of qualitative analysis related to the complexation of metal ions, and, finally, chelation in aqueous coordination chemistry. The paper concludes by tracing the development of inorganic optically active compounds since Werner s time. 

He also concluded that at such concentrations the ions in the vicinity of the electrode are exhausted by reduction and that the current intensity depends mostly on the number of metal ions transported into this space by diffusion. He also pointed out that the position of the wave on the potential axis is characteristic of the reduced species and can be used for qualitative analysis. From occurrence of waves at -0.4 and -0.6 V in solutions prepared from metallic zinc, it was possible to conclude the presence of two impurities, attributed tentatively to indium and gallium. M. Shikata at the same meeting reported (11) the possibility of carrying out the reduction at the D.M.E. in a nonaqueous system - in sodium ethoxide. In the following year the Japanese chemist reported also the first reduction of an organic compound, nitrobenzene (12,13). 

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