Holmium (Metal) by Polarized Light Microscopy


Holmiuim (Chemical symbol Ho) is part of the lanthanide series of elements and is also a rare earth element. It was discovered by a swedish chemist (Per Theodor Cleve) where it's oxide was isolated from rare earth ores in 1878; Interestingly it was also named after the city in Stockholm.

The element itself is a silvery-white metal which is fairly soft. It is far too reactive to be found in its natural state in nature but once isolated it remains relatively stable in dry air at room temperature, that said it does react with water and rusts readily and also burns in air when heated.

How it was done:

Holmium (from an ICP-MS standard) was already dissolved within Nitric acid, so it needed to be concentrated and the acid ‘boiled' off from the solution. Since the solution was around 70%, the boiling off temperature was 121 Degrees C. This solution was placed into a glass container and progressively boiled off over the period of a number of days, as more boiled off the solution was topped up and allowed to boil off again. When only a small amount of Nitric acid was remaining in the bottom of the glass vial it was pipette onto a glass slide and further dried before being imaged by microscopy.


The image was then captured using my normal polarized microscopy setup, which included;

Because the depth of field is relatively small, some images did require focus stacking which is where Helicon Remote & Focus came into the picture (pardon the pun).

Images: (Click to enlarge)


Nitric acid is EXTREAMLY hazardous, and as such should not be worked with without significant personal protective equipment and of course knowledge. All work conducted with these acids, and hazardous materials was conducted with full PPE in addition to in fume cupboards.

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