Hi.

A drop of vinegar tells if magnesium or aluminium. Is there a simple way to tell if it is bronze or brass ?

Bronze is a alloy of copper and tin, brass is a alloy of copper and zinc.

With a drop of hydrochloric or sulfuric acid zinc will react with it, create hydrogen bubbles. Tin and copper show no visible reaction.

With nitric you can develop unsoluble SnO2 with the bronze. Brass will be resolved without residues.

Edited May 24, 2025May 24 by chenbeier

1 hour ago, Externet said:

Hi.

A drop of vinegar tells if magnesium or aluminium. Is there a simple way to tell if it is bronze or brass ?

No. There are too many (ie hundreds) of different alloy compositions under these umbrella headings, and no simple single test will uniquely separate them.

Aluminium bronzes typically contain no intentionally introduced tin. (But some grades do)

Admiralty brasses can contain both zinc and tin in varying amounts.

Gunmetal grades are classed as 'red brass' yet typically contain significantly more tin than zinc.

So there is a certain amount of overlap and the choice of whether to class an alloy as a brass or a bronze can be a matter of convention rather than actual composition.

Any experienced eye can usually recognise the more common (and more familiar) brass alloys by colour (both metal and patina) and context (brasses and bronzes typically have distinct applications).

It takes a certain amount of courage to make a positive identification of many of the bronzes without recourse to eg. X-ray fluorescence spectroscopy.

Edited May 24, 2025May 24 by sethoflagos
Addition

4 hours ago, chenbeier said:

... a drop of ... ... sulfuric acid zinc will react with it, create hydrogen bubbles...

Great! Thanks. I have some diluted sulfuric acid for batteries; hoping will tell some clue, like presence of zinc in the alloy likely being brass.

19 hours ago, chenbeier said:

Bronze is a alloy of copper and tin, brass is a alloy of copper and zinc.

There are brass alloys that contain up to 5% tin:

https://en.wikipedia.org/wiki/Brass#Brass_alloys

19 hours ago, chenbeier said:

With a drop of hydrochloric or sulfuric acid zinc will react with it, create hydrogen bubbles. Tin and copper show no visible reaction.

Copper reacts with concentrated sulfuric acid:

https://www.google.com/search?q=concentrated+sulphuric+acid+copper+reaction

I didn't said to take conc. Sulfuric. As already mentioned a 37% acid like used in car batteries should be efficient. The reaction with copper doesn't matter, because both alloys contain Cu. It is to check is tin or zinc present.

Edited May 25, 2025May 25 by chenbeier

10 hours ago, chenbeier said:

The reaction with copper doesn't matter, because both alloys contain Cu. It is to check is tin or zinc present.

But won't a significant number of bronze alloys yield a false positive for this test? I'm thinking in particular of most aluminium bronzes and gunmetals.

And perhaps a word of caution against employing aggressive bucket chemistry on materials that can have significant lead and arsenic content?

Aluminium of course will give a wrong result. Arsenic and lead has no impact on the result.

The question is what kind of sample has Externet. Maybe it's a coin or a Statue.

These probably don't contain Aluminium.

Edited May 26, 2025May 26 by chenbeier