10x – A piece of very soft 99.9% pure Indium metal from a larger bead that has an oxidized surface.

25x – A magnified view of same piece of Indium as shown in previous image that has been partially digested in 1 drop of HNO3 & 1 drop of H2O.
The metal has become silvery white and is very similar as silver in color.

10x – The Indium metal was removed from the nitric acid solution and was gently brought to dry, creating this super-saturated amorphous deposit.

There was an odd faint odor rising from the vapors as the solution was brought to dry, which kinda resembled turpentine or fuel oil. Of course this is an inaccurate diagnosis of the odor, but I cannot seem to get a handle on a descriptive definition. Furthermore, there is a strange taste in the mouth that does not go away.

This dried deposit absorbed moisture from the room air and again assumed an oily appearance on the glass slide.

10x – To the above semi-dry oily solution 1 drop of HNO3 and 1 drop of H2O was added and this single crystal of K2Cr2O7 (potassium dichromate) was inserted.
No precipitate formed.

10x – Because no precipitate formed in the previous K2Cr2O7 insertion the solution was gently heated to almost dry.
The resultant formation is obviously of no value in determining the presence of Indium in a nitric acid solution.

Because Indium dissolves in hydrochloric acid a few tests were conducted in this acidic medium to provide comparisons.

10x – After dissolving a piece of Indium in HCl a single crystal of K2Cr2O7 was inserted into the HCL solution.
No precipitant formed as the potassium dichromate slowly dissolved.
Heat was gently applied to glass slide till the solution appeared dry, which formed this interesting image.

10x – It did not take but a few moments when the apparently dry solution began absorbing moisture from the room and thus began re-dissolving.

Indium dissolved in HCl seems to behave like In dissolved in HNO3 & H2O. In other words, the solution does not really come to dry. Instead it remains as a thin oily film on the glass slide.

10x – Eventually what appeared as a dry solid area re-dissolves and re-assumes the oily appearance..

Note: KI in a nitric acid solution produces no precipitation and is obviously not a reagent to determine the presence of Indium in this acidic medium.
However, because Indium dissolves in concentrated HCl – potassium iodide was tried in this acidic medium as the next 2 images illustrate.

10x – A piece of Indium was dissolved in concentrated HCl.
No precipitant formed, so heat from a cigarette lighter flame was gently applied to the glass slide holding the solution, which eventually appeared dry and creating this image.

10x – This image of the inserted KI into the HCl solution of dissolved Indium was captured just before the it disappeared.Obviously KI is not a reagent to use for the determination of Indium in HCl.

Note: Indium dissolved in HCl also produced the same odor and persistent taste that Indium does when heat is used to dry the solution in the nitric acid.

It’s apparent that other reagents are required to indicate the presence of Indium in either Nitric or Hydrochloric solutions. Nevertheless, these tests show hints to be aware of.

10x – This toothpick tip was inserted in the original nitric acid solution that had digested some of the Indium.
This white toothpick tip clearly illustrates that no metal was reduced.

40x – A magnified view of the preceding re-ignited image.

Finally, for now, Indium when dissolved is known to wet glass. However, I have seen no evidence on any of the glass slides used during these micro-chems.