40x – A 1/16th long piece of copper wire that was pre-cleaned in dilute nitric acid.

40x – The copper wire fragment submerged in 1 drop water & 1 drop nitric.
The digestive action of this acidic solution produces this greenish color very quickly.

20x – A reduced magnified image of preceding laying within the glass slide’s concave (depression) area that contains the solution.
The white specs are trash particles (lint) laying under the glass slide.

10x – Same solution as above images, but on a white background to better illustrate solution color as the solution via external heat begins to dry.

10x – Because the solution’s volume has been significantly reduced and the blue colors have formed the black microscope stage background allows a better visual perspective than white.

30x – A magnified view of the preceding image to better illustrate crystal structures. Higher magnification fails to clarify these forming structures.

10x -- This image shows what happens when the same copper wire fragment after being well rinsed is subjected to concentrated HCl. There is only weak acid attack of the copper.
Obviously hydrochloric acid is not a particularly good acid for dissolving copper.

30x – A single crystal of K2Cr2O7 added to the copper nitrate solution. Some orange-red precipitation.

20x – The total area of the potassium dichromate precipitation.
My opinion is that K2Cr2O7 is not a great reagent for declaring the presence of Cu in a nitric acid solution. Yet, this image does show a possible sign to be aware of, and is part of the purpose in presenting here.

20x – A single crystal of KI inserted into the nitric solution that has been diluted with 2 additional drops of water to hopefully minimize any Iodine reaction with the nitric acid.

When this KI crystal was introduced there was an immediate violent reaction suggesting Iodine was trying to be reduced. Obviously, according to the image Iodine was not completely reduced. If the Iodine was reduced there would be zillions of tiny black pointed crystals laying all over this area of the glass slide.

30x – Add ed 2 more drops of water and inserted another KI crystal. Again there was a definite reaction, but also this precipitation. Many similar tests need to be conducted using KI before any conclusions can be generated.
After sitting for 2 hours this red-orange and touches pink-brown turned all white.

A Sodium Chloride crystal (NaCl or table salt without any Iodine) was inserted into a solution made like the above on another glass slide. No precipitation and the NaCl crystal completely and quickly dissolved.

10x – This toothpick tip was inserted into the original concentrated acidic solution and when nearly dry it was ignited.
With nitric acid it is not necessary for the toothpick to be dry, for the nitric acid facilitates burning and can generate very high localized temperatures. A small bead of black grunge began forming at tip.

10x – The toothpick has burned a considerable length. The toothpick has not been moved from the previous position.

40x – Upon reheating the toothpick tip under the cirgareet lighter flame a small bleb of black metallic substance formed. Small flecks of copper can be barely be seen at the tip. Subsequent nitric acid digestion proves this toothpick tip to be copper metal.

All the spots within the visual image area is due to a dirty lens protective cover.
When conducting microchems, especially if heat is applied to the solution vapor form and quickly stick onto whatever is close by. Thus, over time these tiny spots build-up into annoyances that demand removal from any optics.

Plating copper onto iron.

10x – A nitric solution (1 drop HNO3 + 3 drops H2O) that has already dissolved some of the piece of copper shown at right in image.
A common 8 penny nail resting on the glass slide above the digested copper solution that will be partially submerged into the shown solution.
The nail was pre-cleaned by dipping in concentrated HCl for a few seconds, then rinsed well and wiped dry.

This is a very good way to help prove the existence of copper in a nitric acid solution that is slightly dilute. If there is much copper it will almost instantly plate onto the nail as the acidic solution digests some of the iron.

10x – The nail shown above was quickly dipped into the illustrated solution and removed and turned over to show the copper plating.
This was and still is a way to retrieve copper from acidic solutions on a commercial scale and has been utilized for centuries by many cultures.

Copper can also be used to extract Mercury from a dilute nitric acid solution.

10x –. A piece of copper wire was pre-cleaned by dipping on a concentrated solution of nitric acid then thoroughly rinsed and wiped dry.

10x – The copper wire was laid in a diluted solution of nitric acid that had dissolved a small amount of Mercury.
Metallic mercury is quickly reduced onto the copper from the acidic solution.

40x – Mercury is reducing (plating) out on to the copper wire.
The air bubbles indicate that the solution is still acidic and dissolving some of the copper.

50x – This magnified view shows the actual Mercury metal beads that have reduced that appeared to be plating the Copper in previous image.