[SADI]

Hi,
Im an ENT specialist trying to find out what levels of copper, nickel, zinc and tin are released from ingested coins exposed to gastric acid.
Could someone tell me what volume of 0.15N HCl (post-prandial gastric acid equivalent) I need for an experiment running a maximum 7 days to ensure that saturation is not reached for these metals or acid used up?

[Mitch]

Well, only nitric acid will be able to remove the Copper from a coin.

[jdurg]

Well, only nitric acid will be able to remove the Copper from a coin.

Yeah, but hydrochloric acid is able to remove any oxidation or 'tarnish' present on the coin, so in a way there will be copper ions in solution as a result.

[SADI]

Thanks for answering so quickly.
No nitric acid in the stomach so no point in testing for copper at all?

[AWK]

This is much complex problem than can be thought. Theoretically, HCl easily dissolves Sn, Zn, and very slowly Ni. But during 7 days all metals (if pure) can be dissolve by HCl because of oxygen from air can do as oxidizer. Moreover, alloys can be more or less resistant to acids than pure metals. Sometimes even a small change of an alloy composition can dramatically change the resistance to acids.

[SADI]

The coins (UK Sterling) being tested are:
1 pound coin - Nickel brass (70% Cu, 5.5% Ni, 24.5%Zn)
10 pence coin - Cupro Nickel (75%Cu, 25%Ni)
2 pence coin - Copper plated steel (97% Cu, 2.5%Zn, 0.5%Sn)

15 to 16% oxygen in stomach gas so reactions could occur.

What about these alloys?