Metal objects chemical analysis

Chemical analysis of the metal can serve various purposes. For the determination of the metal-alloy composition, a variety of techniques has been used. In the past, wet-chemical analysis was often employed, but the significant size of the sample needed was a primary drawback. Nondestmctive, energy-dispersive x-ray fluorescence spectrometry is often used when no high precision is needed. However, this technique only allows a surface analysis, and significant surface phenomena such as preferential enrichments and depletions, which often occur in objects having a burial history, can cause serious errors. For more precise quantitative analyses samples have to be removed from below the surface to be analyzed by means of atomic absorption (82), spectrographic techniques (78,83), etc. 

The objective of this monograph is to include all major studies of metal ions in their aqueous solutions as well as some other important studies in their zerovalent metallic state or in alloys, since the nanoparticles of many of these metals have become too important. Besides, the study of the precipitation of metal ions in aqueous solutions, upon sonication, which has been carried out in our laboratory, would also be discussed. Some of such data include unpublished work. The sequence of metallic ions in this chapter are as they come in the sequence of wet chemical analysis of basic radicals, besides the cationic charge has been kept in mind to make groups and sequences that follow the detailed description. 

The analysis of metal objects of the type discussed here invariably poses a number of questions to the chemical analyst. There are two major sources of difficulty ... 

Proton activation analysis (PAA) provides chemical composition of the materials at a depth of 300-500 pm under the irradiated surface. This technique has been used in the study of metallic objects such as ancient coins [27]. 

Study of a metallic object might involve the following determinations (a) major and trace metal content by chemical analysis ... 

Metals and alloys are in principle good materials for SIMS analysis. They are highly electric conductive materials and can easily be handled so as to obtain clean, flat, and smooth analyzable surfaces, and they are also usually ultrahigh-vacuum-friendly. However, archaeological and/or artistic metal objects do not always possess all of these properties due to degradation processes, which may chemically modify the external surface and deep regions of the samples. Nonconductive patinas and infiltrated compounds may often form as a result of long burial in soil or exposure to the atmosphere, and these have very different characteristics compared with those observed for metal materials. 

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