Removing Tarnish from Silver Coins
By: Andrew Spevacek 2004
Introduction:
In our trials we first wanted to complete the tarnishing process of silver coins. Next we
wanted to know whether it is the metal plate or the powder added to the water that makes
the Quicksilver Kit a better tarnish remover. Thus, our purpose was to test the tarnish
removing kit against our own methods of removing silver, by combining sodium
bicarbonate (NaHCO3) and sodium chloride (NaCl). After testing these two options we
wanted to determine whether the metal plate or the powder added to the water that makes
the kit a better tarnish remover and what this part of the kit was made out of. Our
hypothesis is that it is the Quicksilver Activator solution that is added to the water makes
the kit a better tarnish remover.
Background:
When silver tarnishes, it combines with sulfur and creates silver sulfide. This reaction
follows the equation below:
2Ag + H2S ---> Ag2S + H2
We then went about using this information to tarnish our silver coins. We used the
naturally occurring source of sulfur that is found in the whites of eggs when hard-boiled.
These egg whites, when hard-boiled and left un-refrigerated, provided the necessary
sulfur levels to tarnish our silver.
We then used a chemical reaction to turn the silver sulfide back into silver. We did this
by reacting silver sulfide with aluminum, and because silver sulfide is attracted more to
aluminum, the sulfur atoms will be transferred from the silver to the aluminum. The
reaction follows the formula below (1).
3 Ag2S +
silver
sulfide
2 Al
--> 6 Ag
aluminum
silver
+
Al2S3
aluminum
sulfide
This reaction is called an electrochemical reaction and follows a set of equations. First is
the oxidation reaction (2)(3):
Al°(s) -> Al+3(aq) + 3eNext is the reduction reaction:
3e- + 3 Ag+ --> 3 Ag°(s)
And finally comes the complete oxidation redox reaction:
Al°(s) + 3 Ag+ ---> Al+3 + 3 Ag°(s)
This reaction has been proven to be the best method of removing tarnish from silver
because, along with removing the tarnish, because it re-plates the silver (2)(4).
In an electrochemical reaction tiny electrical current flows between the silver and
aluminum when they come in contact while they are immersed in the solution (1).
After removing the tarnish, the next step is to determine whether is it the plate or the
Quicksilver Powder that makes the kit a better tarnish remover. First comes the process
of measuring the pH of sodium bicarbonate (NaHCO3), Quicksilver Activator, sodium
carbonate monohydrate (Na2CO3 H2O), sodium carbonate (Na2CO3 10H2O), and sodium
carbonate anhydrous (Na2CO3). The chemistry behind this test includes knowing the pH
and comparing the results of our test. pH is the measurement of the acidic nature of the
substance being tested and is a property unique to each substance (5).
The second test we used was titrating the five substances mentioned above to check our
results in our pH experiment. The chemistry behind this test includes reacting the five
basic substances with and acid, in this case 1.0 M HCl, until the base was neutralized (4).
Below are the reactions that take place between the bases and the 1.0 M HCl acid.
Sodium bicarbonate:
NaHCO3(s) + HCl(aq) ––> NaCl(aq) + HOH(l) + CO2(g)
Sodium carbonate monohydrate:
NaHCO3(s) HOH + HCl(aq) ––> NaCl(aq) + 2HOH(l) + CO2(g)
Sodium carbonate decahydrate:
NaHCO3(s) 10H2O + HCl(aq) ––> NaCl(aq) + 10HOH(l) + CO2(g)
Sodium carbonate anhydrous:
Na2CO3(s) + 2HCl(aq) ––> 2NaCl(aq) + HOH(l) + CO2(g)
There was also a reaction for Quicksilver Activator, but because we don’t know the
composition of the activator the reaction equation is not shown (4). After finishing these
experiments we compiled the data and made a conclusion. This completes the chemistry
of our project. The steps necessary to replicate our work are shown below.
Procedure:
Part I – Tarnishing Silver
1. We used four coins, similar in date minted, size and shape.
2. We placed each coin in a plastic bag with a hand chopped boiled egg, and left
them to sit overnight at room temperature.
3. We lined an aluminum bread pan with aluminum foil, making sure the metallic
side of the aluminum foil was facing outward.
4. We added 700 mL of water to the bread pan and we heated the water to 60°C.
5. We weighed out 8.0 grams of sodium bicarbonate and 8.0 grams of sodium
chloride.
6. We added these two substances to the heated water, stirring them until they were
fully dissolved.
7. We weighed the tarnished silver and after recording the tarnished silver’s mass,
we placed it, heads up, heated solution.
8. We allowed the coin to sit in the solution for 10.0 minutes, flipping them every
five minutes.
9. We removed the coin from the bath and recorded its mass.
10. We then calculated the percent mass removed by the sodium bicarbonate/sodium
chloride mixture.
11. We then obtained a Quicksilver kit.
12. We tarnished four more silver coins, each similar in size, shape and mint date as
the four used in the first half of the experiment.
13. We then went about weighing the coin, and following the steps on the box to
remove the tarnish
14. We weighed the coins again after removing the tarnish and calculated the percent
mass removed and compared this data to that yielded by the sodium
bicarbonate/sodium chloride mixture.
Part II – pH Testing
1. We collected Quicksilver Activator, sodium carbonate anhydrous, sodium
carbonate, and sodium carbonate monohydrate.
2. We measured out 5.0 grams of each substance
3. We measured out four beakers with 100.0 mL of H2O, at room temperature.
4. We dissolved one of each substance in each beaker
5. We measured the pH of each substance and recorded the measurement.
6. We compared the measurements of each known substance to the Quicksilver
Activator to determine what the Quicksilver Activator was made out of.
Part III – Standardizing the Substances
1. We collected Quicksilver Activator, sodium carbonate anhydrous, sodium
carbonate, and sodium carbonate monohydrate.
2. We measured out 1.0 grams of each substance
3. We put each substance into a separate Erlenmeyer flask, and added about 10 mL
of water.
4. We dissolved each sustance then added an indicator, Methyl Red.
5. We then measured out 100.0 mL of HCl into a burette and titrated the solution
until the base was standardized
6. We recorded this volume and compared them so that we could see the differences
and similarities between the substances.
Results:
Figure 1: Percent Mass Removed During Tarnish Removal
0.500%
0.450%
Percent Mass Removed
0.400%
0.350%
0.300%
Percent Mass Removed: Quicksilver
Method
Percent Mass Removed: Household
Method
0.250%
0.200%
0.150%
0.100%
0.050%
0.000%
1
2
3
4
Coin Number
Represented above is Figure 1. This figure represented the differences between the
percent mass of silver tarnish removed by the Quicksilver method and our household
method. The top line shows the percent mass removed by the Quicksilver kit and in the
four trails. We found that the 0.260%, 0.400%, 0.300% and 0.407% of the mass was
removed by the Quicksilver Kit and 0.027%, 0.057%, 0.048%, and 0.031% of the mass
was removed by our household methods in the four trials respectively. Its purpose was to
display that the Quicksilver method was a better tarnish remover.
pH of of Substance Tested
Figure 2: pH
12
11.5
11
10.5
10
9.5
9
8.5
8
7.5
7
6.5
6
5.5
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Quicksilver Activator
Sodium Carbonate
Anhydrous
Sodium Carbonate
Sodium Carbonate
Monohydrate
Sodium Bicarbonate
Product Tested
Above is graph 2, which represents the pH levels of 4 sodium carbonate products and the
Quicksilver Activator. Quicksilver Activator had a pH of 11.13, Sodium Carbonate
Anhydrous had a pH of 10.94, Sodium Carbonate had a pH of 11.13, Sodium Carbonate
Monohydrate had a pH 10.78, and Sodium Bicarbonate had a pH of 7.98. Figure 2 above
and the data just listed showed that the Quicksilver activator had the same pH as sodium
carbonate and that all the products tested were bases.
Amount of HCl, in mL, used in Titration
Figure 3: Final Volume in mL of HCl used to Neutralize the Base
16
15.5
15
14.5
14
13.5
13
12.5
12
11.5
11
10.5
10
9.5
9
8.5
8
7.5
7
6.5
6
5.5
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Sodium Bicarbonate
Sodium Carbonate
Sodium Carbonate
Anhydrous
Sodium Carbonate
Monohydrate
Quicksilver Activator
Base Being Titrated
Above in Figure 3, the final volume, in mL, of 1.0 M HCl used to neutralize the base was
shown. The volumes that correspond to figure 3 above are as follows: Sodium
Bicarbonate used 11.40 mL of 1.0 M HCl, Sodium Carbonate used 14.60 mL of 1.0 M
HCl. Sodium Carbonate Anhydrous used 13.50 mL of 1.0 M HCl, Sodium Carbonate
Monohydrate used 12.990 mL of 1.0 M HCl, and Quicksilver Activator used 14.90 mL of
1.0 M HCl. Figure 3 and the data above, showed that once again Quicksilver Activator
and sodium carbonate had nearly the same properties.
Conclusion:
In this project we first found that the Quicksilver Kit method was a better tarnish remover
than then our combination of sodium bicarbonate (NaHCO3), sodium chloride (NaCl),
aluminum foil and heated H2O. We next went about finding whether the metal alloy
plate used in the Quicksilver Kit or the Quicksilver Activator powder made the
Quicksilver Kit a better tarnish remover. After conducting a pH test and a titration test
on the Quicksilver Activator powder we were able to conclude that the Quicksilver
Activator powder had different properties than the sodium bicarbonate (NaHCO3) used in
our method. Thus, from these results we were able to deduce that the differences
between the Quicksilver Activator powder and our sodium bicarbonate (NaHCO3) made
a difference in the effectiveness of the Quicksilver Kit compared to our household
method, thus proving our hypothesis correct.
In the section of our project where we were removing tarnish, we tested the commercial
Quicksilver Kit against our sodium bicarbonate (NaHCO3). We tarnished the silver using
a reaction between sulfur and silver, which formed into silver sulfide. We produced the
sulfur necessary to tarnish our silver coins by hard-boiling an egg and chopping up the
eggs whites and leaving them in a plastic bag with our coins over night. In each of our
methods the process of electroplating to remove tarnish was used (refer back to
background chemistry for specific reactions). After putting our silver through the two
methods of removing tarnish, we found that the Quicksilver Kit produced significantly
better results, as can be seen in graph 1 and table 1.
As the concluding part of our project we went about testing the properties of the
Quicksilver activator powder against those of the sodium bicarbonate we used to
determine whether these two products were the same. First we tested the pH of sodium
bicarbonate (NaHCO3), Quicksilver Activator, sodium carbonate monohydrate (Na2CO3
H2O), sodium carbonate decahydrate (Na2CO3 10H2O), and sodium carbonate anhydrous
(Na2CO3). When testing the pH of these products we found that Quicksilver activator
had a pH of 11.13, which was the same as sodium carbonate, while sodium bicarbonate
had a pH of 7.98. Next we went about standardizing the five substances mentioned
above. The equations for standardizing these five substances are shown in the
background chemistry section.
The results of this test showed that sodium bicarbonate was standardized after titrating
11.40 mL of 1.0 M HCl, while the Quicksilver activator was standardized after titrating
14.90 mL of the same 1.0 M HCl. Once again sodium carbonate, which needed 14.60
mL of 1.0 M HCl to standardize, had nearly the same results as the Quicksilver Activator.
From this data we were first able to conclude that the Quicksilver Activator was a better
tarnish remover than the sodium bicarbonate (NaHCO3) and sodium chloride (NaCl)
mixture. Next we found that the Quicksilver Activator was more closely related to
sodium carbonate not the sodium bicarbonate. We then concluded that the Quicksilver
Activator was not the same as the sodium bicarbonate, and these differences, along with
the data on the percent mass of silver tarnish removed, led us to believe the Quicksilver
Kit being more effective than our household method.
In an upcoming project we would suggest more closely monitor the tarnishing of the
silver being used to make sure this remained constant. As for branching out to another
subsection of this experiment, we would test the properties of the metal alloy plate used
in the Quicksilver Kit against those of the aluminum foil used in our household method to
see if differences existed between the two, and if differences existed, did they lead to the
Quicksilver Kit being a better tarnish remover.
Works Cited
1.) SciFun, “Put a Shine on It,” (2003)
http://scifun.chem.wisc.edu/HOMEEXPTS/TARNISH.html> Accessed April 21,
2004
2.) Cooley, William E. Access Science, “Engineering & Materials: Other engineering
Disciplines: Metallurgical engineering.” http://accessscience.com/server3.) Access Science, “Engineering & Materials: Other engineering Disciplines:
Metallurgical engineering.” “Silver.” www.accessscience.com
4.) Fruen, Lois. The Real World of Chemistry, sixth edition. Kendall/Hunt Publishing
Company, Dubuque, Iowa 2002, p 98, 92
5.) J. Hill, Chemistry for Changing Times (Macmillan Publishing Company, New
York, 6th Edition, 1992), p. 212