Qualitative Analysis of Cations and Anions

Experiment 14 Separation and Qualitative Analysis of Cations and Anions... 

Separation and qualitative analysis of cations and anions test tubes, beaker, evaporating dish, funnel, watch glass, mortar and pestle, centrifuge, Pt or Ni test wire... 

Qualitative analysis is the identification of cations and anions in solution. 

Having become familiar with the reactions of cations and anions, the reader should improve his/her skills in qualitative analysis by carrying out special tests and separations. 

Complex ions are formed in solution by the combination of a metal cation with a Lewis base. The formation constant Kf measures the tendency toward the formation of a specific complex ion. Complex ion formation can increase the solubility of an insoluble substance. Qualitative analysis is the identification of cations and anions in solution. 

Qualitative analysis is the identification of cations and anions in solution. It is based largely on the principles of solubility equilibria. 

Qualitative chemistry is an area of chemistry concerned with identifying substances. In Activity 9.1 you will perform a qualitative analysis to detect the presence of certain ions that, in turn, may reveal an art forgery. The ions could come from paints that were not available at the time of the artwork. In this qualitative analysis, metal ions (cations) and nonmetal ions (anions) are reacted with solvents and with each other. Then the cations and anions present are identified by the products produced. In addition, flame tests and pH determinations are used to identify ions. Qualitative analysis is an engaging opportunity for you to develop experience with chemical change and review solubility principles. Nowadays, however, most of the time a chemist analyzes a substance to detect ion content using quantitative analytical computerized instruments. 

II.l INTRODUCTION Before the student attempts to carry out the analytical reactions of the various cations and anions detailed in Chapters III and IV, he should be familiar with the operations commonly employed in qualitative analysis, that is with the laboratory technique involved. It is assumed that the student has had some training in elementary practical chemistry he should be familiar with such operations as solution, evaporation, crystallization, distillation, precipitation, filtration, decantation, bending of glass tubes, preparation of ignition tubes, boring of corks, and construction of a wash bottle. These will therefore be either very briefly discussed or not described at all in the following pages. 

The book begins with a discussion of the basic physico-chemical aspects of reactions utilised in qualitative inorganic analysis. A description of laboratory equipment follows, and operations which include semimicro and micro techniques, and simple electrochemical, spectroscopic and chromatographic methods. The reactions of the most important cations and anions are described, followed by a treatment of systematic qualitative analysis. Sample preparation, dissolution and fusion of insoluble materials are treated in detail. A separate chapter deals with the reactions of less common ions, with guidelines to their separation and identification in the course of systematic analysis. Finally, a simplified course of qualitative analysis is given this chapter will be particularly useful where the time allocated to qualitative analysis is limited. 

Experiments, such as qualitative analysis of ions via precipitation with a cation or anion [3], the isolation of banana (or strawberry) DNA [4], creating a DNA alias [5], coagulation of milk [6], examining reactions for exothermic or endothermic properties [7], follens test for aldehydes [8] and the conversion of copper pennies to silver [9] have been completed by the participating students. 

ICPMS can be used for both qualitative and quantitative trace and ultra trace elemental analysis of inorganics and in isotope ratio determinations. Both cations and anions can be determined. Normally, the sample is introduced in the form of a solution into the plasma, but direct analysis of gaseous or solid sample is also possible. Hence, ICP-MS has grown into a referral technique for the ultra trace analysis of REE in electronic materials, and metallurgical samples. The individual REE concentrations in natural and sea waters are so low and require preconcentration techniques prior to determination by ICP-MS. Separation in addition to preconcentration is also needed as high salt matrix of sea waters results in irreproducible results in ICP-MS analysis of individual REE. 

Both types of problems are common in the different branches of Chemistry. For example, in Qualitative Chemical Analysis one is frequently faced with a solution containing several unknown cations and anions. The analyst must carry out a pre-established series of reactions, and according to the results must rule out or confirm the presence or absence of the more usual cations and anions. This procedure allows the analyst, depending on the results (formation of precipitates, turbidity, colour reactions in the solution, etc.), to deduce the composition of the problem sample. Qearly, this is an example of a causation problem, because the procedure is pre-established, the results are in plain view and the objective is to know what solution composition is compatible with the results obtained (Martinez-Luaces, 2011). 

The presence of physically adsorbed ammonium salts, which did not undergo cation-exchange reactions and preserved their anions, could be confirmed by qualitative analysis of evolved products of degradation [11]. Moreover, a clear indication of free surfactant in commercial organoclays was the presence of chlorine and sulfur, which were detected in organoclays by means of EDX, as well as the presence of two FTIR bands at 1376 and 1340 cm , which were assigned to the covalent sulfate absorption region (R-O-SO2-O-R) in a manner similar to that reported by Dyer [24]. 

A complete system of qualitative analysis is usually restricted to the detection of a complex array of inorganic cations and anions. In principle, schemes are developed to include less common species such as rhenium and tellurate anions, but more often than not attention is concentrated on more common cations such as Na" and Cu + and oxy anions such as S04 and NO. The basis for identifying inor-... 

It is often desirable to perform a test to determine whether a surfactant is present and, if so, whether it is anionic, cationic, or nonionic. There are a number of booklength works of varying age presenting wet chemical methods for qualitative identification of surfactants and other organic compounds (1-3). However, these are not much used because the most convenient tests for qualitative analysis are those which require equipment already in daily use in the laboratory. Recently, this means sophisticated apparatus designed for quantitative analysis. Thus, most of the qualitative chemical tests have been supplanted by molecular spectroscopic analyses, esjjecially IR and MS analyses. 

Konig and Waldorf discuss analysis of hair and body shampoos (32). The shampoo is first evaporated to dryness and extracted with isopropanol or 95% ethanol to separate the surfactant, which is qualitatively identified by IR. The alcohol-insoluble residue is also examined by IR in case a less-soluble surfactant remains there. The alcohol extract is then separated into anionic, cationic, nonionic, and amphoteric surfactant fractions by ion exchange. Anionics can be separated into sulfonates and carboxylates by use of strongly basic anion exchange resins in the Cl" and OH" form, respectively. Anionics are further characterized by TLC. Nonionics are likewise characterized by TLC. Once the components are identified, quantitative analysis is by the usual methods, described elsewhere in this volume. 

These observations obtained from the application of different API techniques are determinative for qualitative and quantitative FIA results in the analysis of non-ionic and ionic surfactants. Therefore, both ionic surfactant types, anionic and cationic surfactant blends, besides a non-ionic AE surfactant blend were examined, recording their FIA-MS and MS-MS spectra from the blends before the spectra were generated from the mixture of all blends. The results, which show considerable variation, will be presented and discussed as follows. 

The chapter emphasizes the superior analytical power of ion chromatography so that it can be used for qualitative and quantitative analysis of common cations, anions and halides in their different forms and matrices in trace and ultra-trace concentrations. Heavy metals separation and detection was also mentioned as well as hydrogen cyanide as an example of inorganic... 

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