Biological Currency
Introduction
Money is very biological—“The root of all evil.” Microscopic and chemical analysis of money will give a new and
more scientific view of money. It also provides a great introductory activity to microscopy. Sorry, no samples
provided!
Concepts
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Field of view • Iodine starch test
Depth of field • Microscopic magnification
Materials
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Money of desired denominations
Ruler, clear mm
Iodine–potassium iodide solution
Slice of potato
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Standard microscope
Slice of apple
Stereo microscope
Safety Precautions
Iodine–potassium iodide solution may be a skin irritant. It will also form its characteristic dark-stained complex with
anything containing starch, including all paper, books, and some clothing. Avoid all contact with skin, clothing, and
lab materials. Wash your hands thoroughly with soap and water before leaving the laboratory. Wear chemical
splash goggles when working with any laboratory chemicals. Please consult current Material Safety Data Sheets for
additional safety, handling, and disposal information.
Procedure
Part I. Big Money
1. Use a stereoscope to examine a one-dollar bill. First use only overhead light to study the bill.
2. Next, direct the light source from under the bill.
3. Study the money as you answer questions 1–5 for Part IA on the Biological Currency Worksheet.
4. Place a clear plastic ruler on top of the bill and view it under the microscope. What is the length of the
Lincoln Memorial in mm? The circular light area seen when looking through the eyepiece is called the field
of view. Now measure the field of view of the microscope. (Measure the diameter from one edge of the
field of view to the opposite edge.) Estimate to the nearest 0.1 mm. Record your measurement and
microscope power at question #6 Part IA of the Worksheet.
5. Now look at the money with a regular monocular
microscope. Use 100X magnification and adjust the
amount of light carefully when focusing your
microscope. Answer question 1, Part IB on the
worksheet.
6. Use the ruler to measure the diameter of the field of
view at low power (100X). The distance from the center
of one line to the center of the next is 1 millimeter
(1000 microns). Use the center of one line as shown in
Figure 1 to estimate your field of view. Estimate the
diameter to the nearest 0.1 mm. Record the
measurement at question 2 and answer questions
Part II. Counterfeit
7. Secure a small slice of potato and a small slice of apple on a paper towel or a Petri dish.
8. Use a Beral-type pipet to place one drop of iodine–potassium iodide solution on the potato and on the
apple. (A dark blue/purple color indicates the presence of starch.)
9. Record the results on your worksheet Part IIA.
10. Use a Beral-type pipet to place a drop of iodine on piece of notebook paper and another drop on a piece
of money. Recordyour results on the worksheet.
11. Answer the questions for Part IIB on the worksheet.
Disposal
Dispose of all items in the trash, except for the money. That needs to be returned to the teacher.
Biological Currency Worksheet
Part I. Big Money
A. High Five (Stereoscope)
1. Using a one dollar bill, find the spider/owl? Whether it really is one of these animals is a mystery?
Describe its location in the space below.
2.
Using a new 10 dollar bill, describe where it says “ten dollars USA The Unites States of America”?
3.
Name five states whose names cannot be found on the five dollar bill?
4.
On the back of the five dollar bill, what is Abraham Lincoln doing in the memorial?
5.
On any bill, what do the two letters stand for at the beginning of the serial number?
6.
Field of view:
a. Magnification ______________
b. Field of view (0.1 mm) ________
B. Higher Ten (Microscope at 100X)
7. Describe in detail two things you saw with 100X magnification that you did not see with the stereroscope.
8.
Make sketches to illustrate what you saw.
9.
Fields of view:
a. Magnification ______________
b. Field of view _______________(0.1 mm) _________________(microns)
10. What happens to the field of view as the magnification increases?
11. Calculate the field of view for 400X based upon your 100X measurement.
Part II. Counterfeit
A. Iodine/Starch Test Results:
Item
+ or –
(+ if color change)
Potato
Apple
Money Paper
Notebook Paper
B. Answer These Questions:
12. What do potatoes and paper have in common?
13. Can you design a simple device to detect counterfeit money printed on regular paper?
14. How might you detect counterfeit money using a microscope?
15. Research where money is printed in the United States? What material is money made out of?
16. What steps are being taken to stop counterfeiting? Describe the changes over the past few years.
17. What is starch and cellulose and where are they found?
18. Write down the chemical formula for starch and cellulose and draw their chemical structure.
19. Using a $1 or a $5, find two items that require a microscope to see clearly. List the denomination and
what you found below.