Analysis furnace, which will reach 3000K these high

Analysis
of Copper in a Penny                                                                
                     Jessica
Rodriguez 

Dr.  Curtis                                                                                                                               
01/24/2018        

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Introduction:

              Copper is a metal that is red and orange in color and
is the chemical element Cu which comes from the Latin word cuprum. Copper has a
high heat and electric conductivity, which is why it is used in a lot of
electrical equipment. Copper is a very versatile metal that can be combined
with a lot of other different metals to become something else, like when you
mix copper and tin to make bronze.  It is
also used in the making of US currency, like the US penny. Pennies used to be
made of nearly pure copper before the year 1982; it was made of 95 percent
copper and only 5 percent zinc. After the year 1982 to the preset it was
changed to 97.5 percent zinc and only 2.5 percent copper.1

To determine the mass percent of copper in a penny, two
methods are used. The first method being atomic absorption spectroscopy, the
second is ultraviolet-visible spectroscopy. Atomic absorption is a technique in
which the absorption of light by free gaseous atoms or ions in a flame, furnace
is used to measure concentration.2

The sample needs to be a liquid that is sent through a
plastic tube which is the hallow cathode then through a heat source. There are
two different types of heat sources, flame and graphite furnace, which will
reach 3000K these high temperatures are needed to turn the liquid into gaseous
atoms. Then the gaseous atoms will go through the monochromator which is an
optical device that will separate the samples wavelengths depending on what
element you are trying to measure and will remove the unwanted elements that
are in the sample. Then the wavelengths will pass through the detector which
will determine the mass percent of the element in the sample and it will show
up on the data readout.  In order for
this to work the sample will need to be dilated so much that it will be at a
parts per million level because at that level the precision of the instrument
will be two percent.

3

 

 

                          

 

 

Figure
1 . Box diagram of an atomic absorption spectrometer

Atomic spectroscopy is very useful in measuring trace
amounts all the way up to major amounts of metal elements. To get the sample
prepared you must make a dilution of 120 mL of 1 M Cu(H2O)62+
in 1%HNO3.

              Ultraviolet-Visible spectroscopy
is the second method used to determine the mass percent of copper in a penny.

 

4
Figure 2. Box diagram of
Ultraviolet-Visible spectroscopy

 “Ultraviolet
and visible (UV-Vis) absorption spectroscopy is the measurement of the
attenuation (weakening of strength) of a beam of light after it passes through
a sample or after reflection from a sample surface.”5 The light that
is used is allows the outer electrons to get excited enough to jump to a higher
energy sublevel.

The instrument has six important steps to go through; it
first goes through a light source which can be either tungsten lamp for visible
light or deuterium for UV light. Then there is the filter which extracts out any
particles, then it goes through the monochromator, which is an optical device
that will separate the samples wavelengths depending on what element you are
trying to measure and will remove the unwanted elements that are in the sample.
The wavelength that comes from the monochromator will go through the beam
splitter so that it can pass through the sample cuvette and the reference
cuvette at the same time. Then it will go through the photo diode and it will
then start the data processing and finally it will go to the data readout.

The sample must be in a liquid form and it has to be
free form particles, even the solvents used needs to be pure because any
particles that get into the instrument will cause the light to scatter and will
give failed results.

The atomic adsorptions spectroscopy will be able to
calculate the mass percent of copper in the penny better than the UV-vis
spectroscopy because it is more sensitive and that entails it being more
accurate. Using both methods will allow data comparison between both methods to
see which is more accurate.

 

Reference

1.     What’s a
Penny Made Of?, By Live Science Staff | June 21, 2016 03:55pm ET, https://www.livescience.com/32401-whats-a-penny-made-of.html

2.     Exploring
chemical analysis, Daniel C. Harris, 2009 
W.H. Freeman and Company

3.     Introduction
to AAS component parts , POSTED ON MAY 8, 2013 BY DR. DEEPAK BHANOT, http://lab-training.com/2013/05/08/introduction-to-aas-component-parts/       

4.     File:Schematic
of UV- visible spectrophotometer.png, 24 November 2016, at 17:19. https://commons.wikimedia.org/wiki/File:Schematic_of_UV-_visible_spectrophotometer.png

5.     Definition
of UV-Vis Absorption Spectroscopy, Copyright © 2017 chemicool.com, https://www.chemicool.com/definition/uv_vis_absorption_spectroscopy_uv_vis.html

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