10x – A small piece of 99.9% gold cut from a larger piece of bullion.

40x – A magnified view of the preceding image.

20x – The same piece of gold as imaged above in 1 drop nitric acid and 3 drops hydrochloric acid, which is commonly known as Aqua-Regia (A-R).
This piece of gold is being attacked or digested by the A-R.
A focused image is not possible, because the air bubbles are moving the piece of gold around on the glass slide.

10x – The piece of gold was removed from the yellow A-R solution and gently heated to dry with a cigarette lighter flame applied to underside of glass slide.
This dried solution produced this ring of semi-dry gold chloride, which if brought to dry with too much heat some of or all the gold would spontaneously reduce to the metallic state.
Drying gold chloride is a method of reducing gold, but if only a little gold is present within a matrix of other dissolved metals it might be very hard to find the particles. Therefore, a variety of various chemicals can be used to precipitate gold from a chloride solution.
1 drop of concentrated HCl was applied to this area where the gold chloride with some nitric acid is almost dry. The purpose of adding one drop (although 2 or 3 drops would be ok) is to drive off, with heat the nitric acid, which cannot be accomplished with one drying. At least 2 more additions of concentrated HCl and heating to almost dry for a total of 3 dries is required to convert the A-R solution to a chloride solution.

10x – This image is of the 2nd drying of the solution, to which another 1 to 3 drops of HCl is added to convert the A-R to a chloride state.
Notice the significant change in the gold chloride.
Another drop of concentrated HCl was added to this semi-dried reddish area.

10x – This is the 3rd drying and faint but noticeable changes of the gold chloride is apparent.
When drying Gold Chloride there is an indescribable, but not unpleasant odor that I find belongs only to gold.

10x – When a single drop of concentrated HCl was added to the previous dried gold chloride it became evident that tiny amounts of the gold chloride had reduced to the metallic state and is floating on top of, as well as laying on slide within the acid.

HCl alone does not attack gold enough to be concerned about.

The next image is adding powdered zinc to the above HCl solution.

20x – Powdered zinc on glass slide.

20x – This image illustrates how the gold chloride acid solution is vigorously attacking the zinc.

The gold chloride was pipetted from the slide and placed on the so that it would slowly come in contact with the zinc powder.

30x – When the zinc was consumed all that remained were these barely visible and one larger rusty-brown to blackish conglomerated particles of gold as seen in next image.

50x – This was the only single mass of gold and it is not actually a single mass, but a collection of tiny gold particles and although visible to the naked eye was still very small.

Zinc is a great method of reducing gold from any dilute or concentrated HCl solutions.

Zinc will not allow the cementation process of gold if any aqua-regia is part of the solution, because the nitric acid dissolves the zinc.