Crucible materials, analysis

Table IV shows the usefulness of SSMS for the analysis of crucible materials used in crystal growth. Samples of fused silica and graphite were analyzed and the Impurities found are listed. The ability to examine all phases of production Is of great help in pinpointing contamination sources.

The crucible material should not induce further reactions or disrupt the reactions that occur during the analysis. The DTA analyses are usually performed on high temperature ranges, gold and platinum being the most commonly used materials for the manufacturing crucibles. When hard tissues are analyzed by DSC at temperatures below 500 °C, the aluminum crucibles are often used [21], The TGA analyses are made in alumina crucibles, which have the advantage that they can be heated up to 1600 °C [23],... 

Figure 2.39. A sketch of a type of differential thermal analysis head is shown in (a). The two small crucibles (internal diameter 4 6 mm) contain the sample (S) and the reference (R, inert material). The junctions of two thermocouples (Ts, 7r) are inserted in the crucibles. They give the temperature of the sample and the AT between sample and reference. The DTA head is inserted inside a furnace (F), the heating and cooling regime of which may be conveniently controlled.

Method 3(when acardite II centralites are present) a)Extract with chlf or methylene chloride ca lOg of finely divided propellant, evap the solvent and weigh the dried extract (wt 1 - centralite + acardite II) b)Treat the extracted material with aq AcOH at pH ca 4 and filter the mixt through cared sintered glass crucible. Rinse the residue, dry it to const wt and weigh(wt 2 = acardite II and wt 1 — wt 2 centralites) c)Continue. the analysis as described in procedures (c) to (g) of Method 4... 

One of the contamination problems that was encountered illustrates the types of problems that occur in this work. A consistently high material balance was being obtained for copper. One of the platinum crucibles had been used before in the analysis of copper-containing materials. Vigorous cleaning procedures had not removed all of the copper. Now, separate virgin platinum crucibles are used for the trace work and contamination from this source has been eliminated. 

Instrumental neutron activation analysis was used to determine concentrations of several major and trace elements in samples of heavily corroded residues found in crucible fragments excavated at Tel Dan, Israel. The residues were mostly hard, metallic phases admixed with nonmetallic inclusions that appeared to be ceramic material from the loose porous interior of the crucible itself The objective was to identify the metals that had been melted in these crucibles. A method is described that attempts to separate nonmetallic and metallic phase data. In comparison to previous reports on analyses of source materials thought to have been used at Dan in this period (Late Bronze II Age-Early Iron I Age 1400-1000 B.C.), high gold concentrations were found. These appear to be correlated to arsenic and antimony concentrations. This finding is discussed in relation to possible changes in the source of tin at this period. 

The primary objective of our research was the analysis of the mixtures of pottery (crucible wall) and corroded metal residue (slags) by INAA in an attempt to provide information on the metals used at Dan. In addition, two small metal fragments, with little or no ceramic adhesion were sampled. All materials were highly corroded and showed various green, grey, and brown encrustations, and a complete absence of obvious metallic surface. 

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