Alkali metals qualitative analysis

Seven chemical reactions were identified from the chemistry syllabus. These chemical reactions were selected because they were frequently encountered during the 2-year chemistiy course and based on their importance in understanding concepts associated with three topics, namely, acids, bases and salts, metal reactivity series and inorganic chemistry qualitative analysis. The seven types of chemical reactions were combustion of reactive metals in air, chemical reactions between dilute acids and reactive metals, neutralisation reactions between strong acids and strong alkalis, neutralisation reactions between dilute acids and metal oxides, chemical reactions between dilute acids and metal carbonates, ionic precipitation reactions and metal ion displacement reactions. Although two of the chemical reactions involved oxidation and reduction, it was decided not to include the concept of redox in this study as students had only recently been introduced to ion-electron... 

They introduced their spectroscope in a paper published in 1860 (S). They emphasized the utihty of the spectroscope as a very sensitive tool for qualitative elemental analysis. They predicted that the tool would be valuable in the discovery of yet unknown elements. They noted that the spectroscope had convinced them of the existence of another alkali metal besides lithium, sodium, and potassium eventually they foimd two—cesium and mbidium. In that 1860 paper, they noted that their instrument could shed light on the chemical composition of the sun and stars—not many years after Auguste Comte wrote that such knowledge was beyond the reach of human beings. 

Qualitative and quantitative analysis of metals emission techniques routine determination of alkali metals absorption technique extends range of metals that may be determined and the sensitivity. 

The variation of solubility with the composition of the solvent has some importance in inorganic qualitative analysis. Though most of the tests are carried out in aqueous solutions, in some cases it is advantageous to apply other substances (like alcohols, ethers, etc.) as solvents. The separation of alkali metals can for example be achieved by the selective extraction of their salts by various solvents. In other cases the reagent used in the test is dissolved in a non-aqueous solvent, and the addition of the reagent to the test solution in fact changes the composition of the medium. 

In qualitative analysis copper is detected by precipitation as cupric sulphide from hydrochloric-acid solutions of its salts. To prevent the formation of a colloidal precipitate, the solution should be hot, and should contain excess of the acid. The sulphide is soluble in hot, dilute nitric acid, and in potassium-cyanide solution, but almost insoluble in solutions of alkali-metal sulphides. It dissolves to some extent in ammonium-sulphide solution. Other aids in the detection of copper are the blue colour of solutions of cupric-ammonia salts the reddish-brown precipitate of cupric ferrocyanide, produced by addition of potassium ferro-cyanide to cupric solutions the formation of an intense purple coloration by the interaction of hydrogen bromide and cupric salts, a very delicate reaction2 the formation of a bluish-green borax bead and the ready isolation of the metal from its compounds by the action of reducers. 

The sulfides of the alkali and alkaline-earth metals are colorless substances easily soluble in water. The sulfides of most other metals are insoluble or only very slightly soluble in water, and their precipitation under varying conditions is an important part of the usual scheme of qualitative analysis for the metallic ions. Many metallic sulfides occur in nature important sulfide ores include FeS, CugS, CuS, ZnS, AggS, HgS, and PbS. 

Excitation of the outer ns electron of the M atom occurs easily and emission spectra are readily observed. We have aheady described the use of the sodium D-line in the emission spectrum of atomic Na for specific rotation measurements (see Section 3.8). When the salt of an alkali metal is treated with concentrated HCl (giving a volatile metal chloride) and is heated strongly in the non-luminous Bunsen flame, a characteristic flame colour is observed (Li, crimson Na, yellow K, lilac Rb, red-violet Cs, blue) and this flame test is used in qualitative analysis to identify the M ion. In quantitative analysis, use is made of the characteristic atomic spectrum in flame photometry or atomic absorption spectroscopy. 

Qualitative analysis Elame photometry is particrflarly useful for the determination of alkali metals and alkaline-earth metals. It provides the basis for flame tests used in qualitative... 

Observations of alkali-metal ion adducts of the type [M+Li]+ [M+Na]+ etc. are common in the desorption ionization (DI) mass spectra of a variety of polar molecules. In fact, alkali-metal ion association reactions are observed with FD ionization, FAB ionization, Cf plasma desorption (PD), secondary ion mass spectrometry (SIMS), MALDI, and ESI. Ion yields can be greatly enhanced by addition of alkali-metal salts to the sample. Particularly for the MALDI analysis of synthetic polymers, metal cations are often intentionally added to enhance signals. A qualitative description of the current understanding of formation mechanism of alkali-metal ion complexes from the condensed phase was presented [75]. Knowledge of the ionization mechanisms is important and helpful from the perspective of increasing the analytical utility of the method. 

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