Steelworks
Metals are analysed by means of steel beads or pearls.
Usually, the liquid sample is poured onto a plate - where the so-called fusion process occurs - than is then subjected to an X-ray flow for fluorescence analysis.
Ferrous alloys, especially if concentrated, stick to platinum (e.g., high furnace slag).
Crucibles with the Pt950 Au30 Rh20 alloy are often used, because adding gold increases the alloy stiffness and makes the crucible sturdier, while rhodium raises the melting temperature of the platinum alloy.
Cement-production
The UNI-EN 196/2 (verify whether this the latest standard) standardises cement test methods, and specifies that crucibles suitable for this type of analysis must be made of platinum or ceramic material, with a capacity of 20 - 25 cc. Platinum, unlike ceramic materials that tend to be more friable, can withstand higher temperatures and resist acids attacks.
They are used for the chemical analysis of the main elements, to determine the loss to fire, sulphates, and the insoluble residue.
To determine the silica content, the material is calcined and then combined with hydrofluoric acid, which makes platinum crucibles, given their acid-resistant properties, the only option for this sort of analyses.
Cement-production factories use several instruments:
- Annealing vessels in tubular ovens and for analysis of fire loss in nitrogen current
- Calcination or annealing capsules
- Lids used to avoid splashes in analyses with acid, especially those with sodium peroxide
- Plates in fusion units that must be perfectly smooth and with a mirror bottom, which should ensure perfect pearls that guarantee the reliability of X-ray fluorescence analysis that would otherwise be distorted.
- Conical crucibles to ease molten material extraction.
The Pt Au alloy is regularly used for analyses in fusion units. This is so because platinum-only crucibles deform more easily compared to those made of PtAu alloy, which confers the crucible higher structural stiffness. In this case, however, we must bear in mind that the X-ray fluorescence analysis may show a peak in gold values.
Paint-production
In this sector, crucibles are used to perform the evaporative analysis of paints with earth, sand or lead, or other calcined materials.
This type of analyses are conducted to verify product density.
Glass-production
Glass paste analysis is carried out to determine the density of colour and that of the paste itself.
In this context, it is common to find Pt90 Rh10 or Pr80 Rh20 alloys. Analyses are conducted on stationary plants fitted with ovens where the glass is constantly melted.
