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Post Your Acid Dip Experiments

 
 
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Pillar of the Community
United States
1547 Posts
 Posted 11/14/2019  3:53 pm Show Profile   Bookmark this topic Add arby96 to your friends list Get a Link to this Message
I purchased a dime taking a chance it might be something special, I was informed it was an acid dipped coin, So I wanted to see which acid would cause this damage. None of these acid baths matched the dime damage I have. These three dimes were in three different acid baths for approx 30 days, Dime one, Muriatic Acid, Muriatic acid did the most damage, It also did more damage to the copper part of the Dime, It weighs in at 1.7 grams. Dime two sat in Sulfuric Acid, This caused the least damage, and weighs in at 2.2 grams, and Dime three sat in Hydrochloric Acid, it changed the appearance of the dime mostly the color, and caused some surface damage. Still none match the dime I have which still has the reeding, and weighs in at 1.1 grams. Now I am not stating my coin is not acid bathed its just I can't duplicate my dime condition with those three acids. On the Muriatic Acid Dime, I can fit my dime between the Obverse and reverse sides, the inner copper has receded far enough that the reeding is completely gone. So I can definitely rule out Muriatic Acid. I don't believe based on my experiment that those other acids caused this damage. Please tell me what you think.





Muriatic Acid


Sulfuric Acid


Hydrochloric Acid








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Edited by arby96
11/14/2019 4:06 pm
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United States
79443 Posts
Pillar of the Community
Canada
2866 Posts
 Posted 11/14/2019  5:27 pm  Show Profile   Bookmark this reply Add oriole to your friends list Get a Link to this Reply
That is quite interesting, in a Stephen King kind of way.
Pillar of the Community
Canada
664 Posts
 Posted 11/14/2019  5:28 pm  Show Profile   Bookmark this reply Add Scissel to your friends list Get a Link to this Reply
I think traditionally for the experiment, Coca Cola is used : phosphoric acid...
Pillar of the Community
United States
1547 Posts
 Posted 11/14/2019  5:57 pm  Show Profile   Bookmark this reply Add arby96 to your friends list Get a Link to this Reply
I will try coca cola next then, I am determined to duplicate my coin. we will see what happens.
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Australia
13197 Posts
 Posted 11/14/2019  6:05 pm  Show Profile   Bookmark this reply Add Sap to your friends list Get a Link to this Reply
Just FYI: "muriatic acid" and "hydrochloric acid" are different names for the exact same chemical - as you will discover if you type "muriatic acid" into Wikipedia. They might be sold under different names at different concentrations.

How acid will react to a coin will also depend on the initial condition of the coin; we haven;t seen the "initial" photographs of the acid-soaked coins. I assume they all looked much the same? It's important in scientific experiments to control the variables, and one variable that's important in chemical reactions is starting conditions. Ideally, you want to take coins with identical levels of preservation - such as taking them all out of mint rolls. Ideally, you'd want to use 1972 coins (or coins of similar date to your "unknown", as the changes in production techniques may also be relevant. You'd also ideally want to include replicates, to make sure one of the coins isn't unusual in some way.

Acid will also behave differently to metals at different strengths. And it is not necessarily a linear progression. Concentrated sulfuric acid will react differently than sulfuric acid that is more dilute, as different chemical reaction occur in concentrated sulfuric acid. To get concentrate sufuric acid to react with metal, you really need to heat it up.

Copper is generally more prone to acid attack than cupronickel alloy, so any strong acid is likely to result in what you have observed: the copper core being eaten away faster than the clad layer, creating a "hollow sandwich" appearance. A weaker acid over a more prolonged period might cause a different reaction. Try phosphoric acid; I believe that does not strongly react with copper, especially oxidized copper.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
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United States
25 Posts
 Posted 11/15/2019  10:27 am  Show Profile   Bookmark this reply Add Safaga to your friends list Get a Link to this Reply
Thank you, @Sap. Very enlightening information.
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